The Development Environment - Integrated Development Environment (IDE):
The Turbo C compiler has its own built-in text editor. The files you create with text editor are
called source files, and for C++ they typically are named with the extension .CPP, .CP, or .C.
The C Developing Environment, also called as Programmer’s Platform, is a screen display
with windows and pull-down menus. The program listing, error messages and other
information are displayed in separate windows. The menus may be used to invoke all the
operations necessary to develop the program, including editing, compiling, linking, and
debugging and program execution.
Invoking the IDE
To invoke the IDE from the windows you need to double click the TC icon
in the directory c:\tc\bin.
The alternate approach is that we can make a shortcut of tc.exe on the desktop. This makes you
enter the IDE interface, which initially displays only a menu bar at the top of the screen
and a status line below will appear. The menu bar displays the menu names and the status line
tells what various function keys will do.
Default DirectoryThe default directory of Turbo C compiler is c:\tc\bin.
Using Menus
If the menu bar is inactive, it may be invoked by pressing the [F10] function key. To select
different menu, move the highlight left or right with cursor (arrow) keys. You can also revoke
the selection by pressing the key combination for the specific menu.
Opening New Window
To type a program, you need to open an Edit Window. For this, open file menu and click
“new”. A window will appear on the screen where the program may be typed.
Writing a Program
When the Edit window is active, the program may be typed. Use the certain key combinations
to perform specific edit functions.
Saving a Program
To save the program, select save command from the file menu. This function can also be
performed by pressing the [F2] button. A dialog box will appear asking for the path and name
of the file. Provide an appropriate and unique file name. You can save the program after
compiling too but saving it before compilation is more appropriate.
Making an Executable File
The source file is required to be turned into an executable file. This is called “Making” of the
.exe file. The steps required to create an executable file are:
1. Create a source file, with a .c extension.
2. Compile the source code into a file with the .obj extension.
3. Link your .obj file with any needed libraries to produce an executable program.
All the above steps can be done by using Run option from the menu bar or using key
combination Ctrl+F9 (By this linking & compiling is done in one step).
Compiling the Source Code
Although the source code in your file is somewhat cryptic, and anyone who doesn't know C
will struggle to understand what it is for, it is still in what we call human-readable form. But,
for the computer to understand this source code, it must be converted into machine-readable
form. This is done by using a compiler. Hence, compiling is the process in which source code
is translated into machine understandable language.
It can be done by selecting Compile option from menu bar or using key combination Alt+F9.
Creating an Executable File with the Linker
After your source code is compiled, an object file is produced. This file is often named with
the extension .OBJ. This is still not an executable program, however. To turn this into an
executable program, you must run your linker. C programs are typically created by linking
together one or more OBJ files with one or more libraries. A library is a collection of linkable
files that were supplied with your compiler.
Compiling and linking in the IDE
In the Turbo C IDE, compiling and linking can be performed together in one step. There are
two ways to do this: you can select Make EXE from the compile menu, or you can press the
[F9] key.
Executing a Program
If the program is compiled and linked without errors, the program is executed by selecting
Run from the Run Menu or by pressing the [Ctrl+F9] key combination.The Development CycleIf every program worked the first time you tried it that would be the complete development
cycle: Write the program, compile the source code, link the program, and run it.
Unfortunately, almost every program, no matter how trivial, can and will have errors, or bugs,
in the program. Some bugs will cause the compile to fail, some will cause the link to fail, and
some will only show up when you run the program.
Whatever type of bug you find, you must fix it, and that involves editing your source code,
recompiling and relinking, and then rerunning the program.
Correcting Errors
If the compiler recognizes some error, it will let you know through the Compiler window.
You’ll see that the number of errors is not listed as 0, and the word “Error” appears instead of
the word “Success” at the bottom of the window. The errors are to be removed by returning to
the edit window. Usually these errors are a result of a typing mistake. The compiler will not
only tell you what you did wrong; they’ll point you to the exact place in your code where you
made the mistake.
Exiting IDE
An Edit window may be closed in a number of different ways. You can click on the small
square in the upper left corner, you can select close from the window menu, or you can press
the [Alt][F3] combination. To exit from the IDE, select
[Alt][X] Combination.EXERCISEExit from the File Menu or press
1. Type the following program in C Editor and execute it. Mention the Error.
void main(void)
{
printf(“ This is my first program in C ”);
}
2. Add the following line at the beginning of the above program. Recompile the
program. What is the output?
#include<stdio.h>
3. Make the following changes to the program. What Errors are observed?
i. Write Void instead of void .
ii. write void main (void);
iii. Remove the semi colon ‘;’.
iv. Erase any one of brace ‘{’ or ‘}’.
In any language there are certain building blocks:
• Constants
• Variables
• Operators
• Methods to get input from user(scanf( ), getch( ) etc.)
• Methods to display output (Format Specifier, Escape Sequences etc.) etc.
Format Specifiers
Format Specifiers tell the printf statement where to put the text and how to display the text.
The various format specifiers are:
%d => integer
%c => character
%f => float etc.
Variables and Constants
If the value of an item is to be changed in the program then it is a variable. If it will not
change then that item is a constant. The various variable types (also called data type) in C are:
int, float, char, long ,double etc they are also of the type signed or unsigned.
Escape Sequences
Escape Sequence causes the program to escape from the normal interpretation of a string, so
that the next character is recognized as having a special meaning. The back slash “\” character
is called the Escape Character”
\n => new line
\t => tab
\b => back space
\r => carriage return
\” => double quotations
\\ => back slash etc.
. The escape sequence includes the following:
Taking Input From the User
The input from the user can be taken by the following techniques: scanf( ), getch( ), getche( ),
getchar( ) etc.
OperatorsThere are various types of operators that may be placed in three categories:
Basic: + - * / %
Assignment: = += -= *= /= %=
(++, -- may also be considered as assignment operators)
Relational: < > <= >= == !=
Logical: && , || , !
EXERCISE
Decision making the if and if-else structure
Normally, your program flows along line by line in the order in which it appears in your
source code. But, it is sometimes required to execute a particular portion of code only if
certain condition is true; or false i.e. you have to make decision in your program. There are
three major decision making structures. The ‘if’ statement, the if-else statement, and the
switch statement. Another less commonly used structure is the conditional operator.
The if statement
The if statement enables you to test for a condition (such as whether two variables are equal)
and branch to different parts of your code, depending on the result or the conditions with
relational and logical operators are also included..
The simplest form of an
if (expression)
statement;
if statement is:
The if-else statement
Often your program will want to take one branch if your condition is true, another if it is false.
If only one statement is to be followed by the if or else condition then there is no need of
parenthesis. The keyword
if (expression)
{ statement/s;
}
else can be used to perform this functionality:
else
{
statement/s;
}
EXERCISE
Decision making the Switch case and conditional operator
Normally, your program flows along line by line in the order in which it appears in your
source code. But, it is sometimes required to execute a particular portion of code only if
certain condition is true; or false i.e. you have to make decision in your program. There are
three major decision making structures. The ‘if’ statement, the if-else statement, and the
switch statement. Another less commonly used structure is the conditional operator.
The switch StatementUnlike if , which evaluates one value, switch statements allow you to branch on any of a
number of different values. There must be break at the end of the statements of each case
otherwise all the preceding cases will be executed including the default condition. The general
form of the switch statement is:
switch (identifier variable)
{
case identifier One: statement;
case identifier Two: statement;
....
case identifier N: statement;
default: statement;
}
Conditional OperatorThe conditional operator ( ?: ) is C’s only ternary operator; that is, it is the only operator to
take three terms.
The conditional operator takes three expressions and returns a value:
(expression1) ? (expression2) : (expression3)
It replaces the following statements of if else structure
If(a>b)
c=a;
else
c=b;
can be replaced by
c=(a>b)?:a:b
This line is read as "If expression1 is true, return the value of expression2; otherwise, return
the value of expression3." Typically, this value would be assigned to a variable.
EXERCISE
Looping constructs in C-Language
Types of Loops
There are three types of Loops:
1) for Loop
i.for loop
ii.nested for loop
2) while Loop
i.while loop
ii.nested while loop
3) do - while Loop
i.do while loop
ii. nested do while loop
Nesting may extend these loops.
The for Loopfor(initialize(optional);condition(compulsory);increment(optio
nal)
{
Body of the Loop;
}
This loop runs as long as the condition in the center is true. Note that there is no semicolon
after the “for” statement. If there is only one statement in the “for” loop then the braces may
be removed. If we put a semicolon after the for loop instruction then that loop will not work
for any statements.
The while Loop
while(condition is true)
{
Body of the Loop;
}
This loop runs as long as the condition in the parenthesis is true. Note that there is no
semicolon after the “while” statement. If there is only one statement in the “while” loop then
the braces may be re moved.
The do-while Loop
do
{
Body of the Loop;
}
while(condition is true);
This loop runs as long as the condition in the parenthesis is true. Note that there is a
semicolon after the “while” statement. The difference between the “while” and the “do-while”
statements is that in the “while” loop the test condition is evaluated before the loop is
executed, while in the “do” loop the test condition is evaluated after the loop is executed. This
implies that statements in a “do” loop are executed at least once. However, the statements in
the “while” loop are not executed if the condition is not satisfied..
EXERCISE
Program in C to Reverse the given string
The Nested for Loop
for(initialize;condition;increment)
{
for(initialize;condition;increment)
{
Body of the loop;
}
}
The inner loop runs as many times as there is the limit of the condition of the external loop.
This loop runs as long as the condition in the parenthesis is true. We can nest many loops
inside as there is the requirement.
The nested while Loopwhile(condition is true)
{
while(condition is true)
{
Body of the loop;
}
Body of the loop;
}
The inner loop runs as many times as there is the limit of the condition of the external loop.
This loop runs as long as the condition in the parenthesis is true. We can nest many loops
inside as there is the requirement.
The Nested do-while Loopdo
{
do
{
body of the loop;
}
while(condition is true);
body of the loop;
}
while(condition is true);
This loop runs as long as the condition in the parenthesis is true. Note that there is a
semicolon after the “while” statement. The difference between the “while” and the “do-while”
statements is that in the “while” loop the test condition is evaluated before the loop is
executed, while in the “do” loop the test condition is evaluated after the loop is executed. This
implies that statements in a “do” loop are executed at least once. The inner loop runs as many
times as there is the limit of the condition of the external loop. This loop runs as long as the
condition in the parenthesis is true. We can nest many loops inside as there is the requirement.
EXERCISE
Program to Print the Pattern:
1
121
12321
1234321
123454321
12345654321
1234567654321
123456787654321
12345678987654321
Debugging and Single-Stepping of C Programs
One of the most innovative and useful features of Turbo C++ is the integration of debugging
facilities into the IDE.
Even if your program compiles perfectly, it still may not work. Such errors that cause the
program to give incorrect results are called Logical Errors. The first thing that should be done
is to review the listing carefully. Often, the mistake will be obvious. But, if it is not, you’ll
need the assistance of the Turbo C Debugger.
One Step at a Time
The first thing that the debugger can do for you is slow down the operation of the program.
One trouble with finding errors is that a typical program executes in a few milliseconds, so all
you can see is its final state. By invoking C++’s single-stepping capability, you can execute
just one line of the program at a time. This way you can follow where the program is going.
Consider the following program:void main(void)
{
int number, answer=-1;
number = -50;
if(number < 100)
if(number > 0)
answer = 1;
else
answer = 0;
printf(“answer is %d\n”, answer);
}
Our intention in this program is that when number is between 0 and 100, answer will be 1,
when the number is 100 or greater, answer will be 0 , and when number is less than 0,
answer will retain its initialized value of –1. When we run this program with a test value of
-50 for number, we find that answer is set to 0 at the end of the program, instead of staying –1
We can understand where the problem is if we single step through the program. To do this,
simply press the [F7] key. The first line of the program will be highlighted. This highlighted
line is called the run bar . Press [F7] again. The run bar will move to the next program line.
The run bar appears on the line about to be executed. You can execute each line of the
program in turn by pressing [F7]. Eventually you’ll reach the first
if (num < 100 )
This statement is true (since number is –50); so, as we would expect the run bar moves to the
second if statement:
if(num>0)
This is false. Because there’s no else matched with the second if, we would expect the run bar
to the printf( ) statement. But it doesn’t! It goes to the line
answer = 0;
Now that we see where the program actually goes, the source of the bug should become clear. The else goes with the last if, not the first if as the indenting would lead us to believe. So, the else is executed when the second need to put braces around the second if statement is false, which leads to erroneous results. We need to put braces around the second if, or rewrite the program in some other way.
Resetting the Debugger
Suppose you’ve single stepped part way through a program, and want to start over at the
beginning. How do you place the run bar at the top of the listing? You can reset the
debugging process and initialize the run bar by selecting the Program Reset option from the
Run menu.
WatchesSingle stepping is usually used with other features of the debugger. The most useful of these
is the watch (or watch expression). This lets you see how the value of variable changes as the
program runs. To add a watch expression, press [Ctrl+F7] and type the expression.BreakpointsIt often happens that you’ve debugged part of your program, but must deal with a bug in
another section, and you don’t want to single-step through all the statements in the first part to
get to the section with the bug. Or you may have a loop with many iterations that would be
tedious to step through. The way to do this is with a breakpoint. A breakpoint marks a
statement where the program will stop. If you start the program with [Ctrl][F9], it will execute
all the statements up to the breakpoint, then stop. You can now examine the state of the
variables at that point using the watch window.
Installing breakpoints
To set a breakpoint, first position the cursor on the appropriate line. Then select Toggle
Breakpoint from the Debug menu (or press [Ctrl][F8]). The line with the breakpoint will be
highlighted. You can install as many breakpoints as you want. This is useful if the program
can take several different paths, depending on the result of if statements or other branching
constructs.
Removing Breakpoints
You can remove a single breakpoint by positioning the cursor on the line with the breakpoint
and selecting Toggle breakpoint from the Debug menu or pressing the [Ctrl][F8] combination
(just as you did to install the breakpoint). The breakpoint highlight will vanish.
You can all set Conditional Breakpoints that would break at the specified value only.
Functions in C-Language programming
Functions are used normally in those programs where some specific work is required to be
done repeatedly and looping fails to do the same.
Three things are necessary while using a function.
i. Declaring a function or prototype:
The general structure of a function declaration is as follows:
return_type function_name(arguments);
Before defining a function, it is required to declare the function i.e. to specify the function
prototype. A function declaration is followed by a semicolon ‘ ;’. Unlike the function
definition only data type are to be me ntioned for arguments in the function declaration.
ii. Calling a function:
The function call is made as follows:
return_type = function_name(arguments);
iii. Defining a function:
All the statements or the operations to be performed by a function are given in the function
definition which is normally given at the end of the program outside the main.
Function is defined as follows
return_type function_name(arguments)
{
Statements;
}
There are certain functions that you have already used e.g: getche( ), clrscr( ), printf( ), scanf( )
etc.
There are four types of functions depending on the return type and arguments:
• Functions that take nothing as argument and return nothing.
• Functions that take arguments but return nothing.
• Functions that do not take arguments but return something.
• Functions that take arguments and return something.
A function that returns nothing must have the return type “void”. If nothing is specified then
the return type is considered as “int”.
Preprocessor Directives
Preprocessor directives are actually the instructions to the compiler itself. They are not
translated but are operated directly by the compiler.
The most common preprocessor directives are
i. include directive
ii. define directive
i. include directive: The include directive is used to include files like as we include header
files in the beginning of the program using #include directive like
#include<stdio.h>
#include<conio.h>
ii. define directive: It is used to assign names to different constants or statements which are
to be used repeatedly in a program. These defined values or statement can be used by main or
in the user defined functions as well.
They are used for
a. defining a constant b.
defining a statement
c. defining a mathematical expression
for example
#define pi 3.142
#define p printf(“enter a new number”);
#define for(a) (4/3.0)*pi*(a*a*a);
They are also termed as macros.
Arrays in C (one dimensional)
An array is a collection of data storage locations, each of which holds the same type of data.
Each storage location is called an element of the array. You declare an array by writing the
type, followed by the array name and the subscript. The subscript is the number of elements in
the array, surrounded by square brackets. For example,
long LongArray[25];
declares an array of 25 long integers, named Long Array. When the compiler sees this
declaration, it sets aside enough memory to hold all 25 elements. Because each long integer
requires 4 bytes, this declaration sets aside 100 contiguous bytes of memory.
Arrays in C (Multidimensional)
A Multidimensional array is a collection of data storage locations, each of which holds the
same type of data. Each storage location is called an element of the array. You declare an
array by writing the type, followed by the array name and the subscript. The subscript is the
number of elements in the array, surrounded by square brackets. For example,
int a[5][10]
declares an array of 50 integers, named a. Its declaration shows that array a comprises of 5
one dimensional arrays and each one dimensional array contains 10 elements.
When the compiler sees this declaration, it sets aside enough memory to hold all 50 elements.
Because each integer requires 2 bytes, this declaration sets aside 100 contiguous bytes of
memory.Learning Text and Graphics modes of display in C
There are two ways to view the display screen in Turbo C graphics model:
• The Text Mode
• The Graphics Mode.
The Text Mode
In the Text Mode, the entire screen is viewed as a grid of cells, usually 25 rows by 80
columns. Each cell can hold a character with certain foreground and background colors (if the
monitor is capable of displaying colors). In text modes, a location on the screen is expressed
in terms of rows and columns with the upper left corner corresponding to (1,1), the column
numbers increasing from left to right and the row numbers increasing vertically downwards.
The Graphics Mode
In the Graphics Mode, the screen is seen as a matrix of pixels, each capable of displaying one
or more color. The Turbo C Graphics coordinate system has its origin at the upper left hand
corner of the physical screen with the x-axis positive to the right and the y-axis positive going
downwards.The ANSI Standard CodesThe ANSI – American National Standards Institute provides a standardized set of codes for
cursor control. For this purpose, a file named ANSI. sys is to be installed each time you turn
on your computer. Using the config.sys file, this job is automated, so that once you’ve got
your system set up, you don’t need to worry about it again.
To automate the loading of ANSI . sys follow these steps:
i. Find the file ANSI.sys in your system. Note the path.
ii. Find the config.sys file. Open this file and type the following:
DEVICE = path_of_ANSI.sys
iii. Restart your computer.
All the ANSI codes start by the character \x1B[ after which, we mention codes specific to
certain operation. Using the #define directive will make the programs easier to write and
understand.
Structures
If we want a group of same data type we use an array. If we want a group of elements of
different data types we use structures. For Example: To store the names, prices and number of
pages of a book you can declare three variables. To store this information for more than one
book three separate arrays may be declared. Another option is to make a structure. No
me mory is allocated when a structure is declared. It simply defines the “form” of the
structure. When a variable is made then memory is allocated. This is equivalent to saying that
there is no memory for “int” , but when we de clare an integer i.e.
is allocated.
The structure for the above mentioned case will look like
Struct books
{char bookname[20];
float price;
int pages;}
struct book[50];
the above structure can hold information of 50 books.
EXERCISE
1. Write a program to maintain the library record for 100 books with book name,
author’s name, and edition, year of publishing and price of the book.
2. Write a program to make a tabulation sheet for a class of 50 students with their names, seat
nos, marks, percentages and grades.
Pointers in C-Language
A pointer provides a way of accessing a variable without referring to the variable
directly. The address of the variable is used.
The declaration of the pointer
int *p;
means that the expression *p is an int. This definition set aside two bytes in which to
store the address of an integer variable and gives this storage space the name p. If
instead of int we declare
char * p;
again, in this case 2 bytes will be occupied, but this time the address stored will b e
pointing to a single byte.
Pointers with arrays and function
A pointer is the most effective tool to pass an array to a function.
If pointers are involved than a function can return more than one values at a time.
We have to pass only the address and size of the array to the function and we can make as
many changes in the function as we want. for example if we want to add 5 in each array
element using functions.
void add(int *,int);
void main(void)
{int s[10],i;
printf(“enter ten integers”);
for(i=0,i<10,i++)
{printf(“\n enter integer no %d :”,i+1);
scanf(“%d”,&s[i]);
}
add(s,10);
for(i=0,i<10,i++)
{printf(“\n integer no %d :%d”,i+1,s[i]);
}
}
void add(int *p,int x)
{int j;
for (j=0;j<x;j++)
{
*p=*p+5;
p++;
}
}
Similarly string arrays and multidimensional arrays can also be passed to functions by
their addresses and size.
1. Write a program to pass an integer array of 10 elements to a function which returns the
same array after sorting it in descending order. Print the array.
Filing in C-Language
Data filesMany applications require that information be “ written & read” fro m an auxiliary
storage device.
This information is written in the form of Data Files .
Data files allow us to store information permanently and to access and alter that
information whenever necessary.
Types of Data filesStandard data files .(stream I/O)
System data files. (low level I/O)
Standard I/O
Easy to work with, & have different ways to handle data.
Four ways of reading & writing data:
1. Character I/O.
2. String I/O.
3. Formatted I/O.
4. Record I/O.
File Protocol
1. fopen
2. fclose
fopen:-
Syntax:It is used to open a file .
fopen (file name , access-mode ).
“r” open a file for reading only.
“w” open a file for writing.
“a” open a file for appending .
“r+” open an existing file for reading & writing.
“w+” open a new file for reading &writing.
“a+” open a file for reading & appending & create a new file if it does exist.
Example:-#include <stdio.h>
main
{
FILE*fpt;
fpt = fopen (“first.txt”,”w”);
fclose(fpt);
}
Establish buffer area, where the information is temporarily stored before being
transferred b/w the computer memory & the data file.
file is a special structure type that establishes the buffer area.
fpt is a pointer variable that indicates the beginning of buffer area.
fpt is called stream pointer.
fopen stands for File Open.
A data file must be opened before it can be created or processed
Standard I/O:
Four way s of reading and writing data:
Character I/O.
String I/O.
Formatted I/O.
Record I/O.
Character I/O:
In normal C program we used to use getch, getchar and getche etc.
In filling we use putc and getc.
putc( );
It is used to write each character to the data file.
Putc requires specification of the stream pointer *fpt as an argument.
Syntax:putc(c, fp);
c = character to be written in the file .
fp = file pointer .
putch or putchar writes the I/P character to the consol while putc writes to the file.
Example (1):Reading the Data File:#include < stdio.h >
main( )
{
FILE*fpt;
Char c;
fpt = fopen ( “ star.dat”,”r”);
if( fpt = = NULL);
printf( “Error- cant open”);
else
do
putchar(c=getc(fpt) );
while(c!=‘\n’ );
fclose( fpt );
}
The Turbo C compiler has its own built-in text editor. The files you create with text editor are
called source files, and for C++ they typically are named with the extension .CPP, .CP, or .C.
The C Developing Environment, also called as Programmer’s Platform, is a screen display
with windows and pull-down menus. The program listing, error messages and other
information are displayed in separate windows. The menus may be used to invoke all the
operations necessary to develop the program, including editing, compiling, linking, and
debugging and program execution.
Invoking the IDE
To invoke the IDE from the windows you need to double click the TC icon
in the directory c:\tc\bin.
The alternate approach is that we can make a shortcut of tc.exe on the desktop. This makes you
enter the IDE interface, which initially displays only a menu bar at the top of the screen
and a status line below will appear. The menu bar displays the menu names and the status line
tells what various function keys will do.
Default DirectoryThe default directory of Turbo C compiler is c:\tc\bin.
Using Menus
If the menu bar is inactive, it may be invoked by pressing the [F10] function key. To select
different menu, move the highlight left or right with cursor (arrow) keys. You can also revoke
the selection by pressing the key combination for the specific menu.
Opening New Window
To type a program, you need to open an Edit Window. For this, open file menu and click
“new”. A window will appear on the screen where the program may be typed.
Writing a Program
When the Edit window is active, the program may be typed. Use the certain key combinations
to perform specific edit functions.
Saving a Program
To save the program, select save command from the file menu. This function can also be
performed by pressing the [F2] button. A dialog box will appear asking for the path and name
of the file. Provide an appropriate and unique file name. You can save the program after
compiling too but saving it before compilation is more appropriate.
Making an Executable File
The source file is required to be turned into an executable file. This is called “Making” of the
.exe file. The steps required to create an executable file are:
1. Create a source file, with a .c extension.
2. Compile the source code into a file with the .obj extension.
3. Link your .obj file with any needed libraries to produce an executable program.
All the above steps can be done by using Run option from the menu bar or using key
combination Ctrl+F9 (By this linking & compiling is done in one step).
Compiling the Source Code
Although the source code in your file is somewhat cryptic, and anyone who doesn't know C
will struggle to understand what it is for, it is still in what we call human-readable form. But,
for the computer to understand this source code, it must be converted into machine-readable
form. This is done by using a compiler. Hence, compiling is the process in which source code
is translated into machine understandable language.
It can be done by selecting Compile option from menu bar or using key combination Alt+F9.
Creating an Executable File with the Linker
After your source code is compiled, an object file is produced. This file is often named with
the extension .OBJ. This is still not an executable program, however. To turn this into an
executable program, you must run your linker. C programs are typically created by linking
together one or more OBJ files with one or more libraries. A library is a collection of linkable
files that were supplied with your compiler.
Compiling and linking in the IDE
In the Turbo C IDE, compiling and linking can be performed together in one step. There are
two ways to do this: you can select Make EXE from the compile menu, or you can press the
[F9] key.
Executing a Program
If the program is compiled and linked without errors, the program is executed by selecting
Run from the Run Menu or by pressing the [Ctrl+F9] key combination.The Development CycleIf every program worked the first time you tried it that would be the complete development
cycle: Write the program, compile the source code, link the program, and run it.
Unfortunately, almost every program, no matter how trivial, can and will have errors, or bugs,
in the program. Some bugs will cause the compile to fail, some will cause the link to fail, and
some will only show up when you run the program.
Whatever type of bug you find, you must fix it, and that involves editing your source code,
recompiling and relinking, and then rerunning the program.
Correcting Errors
If the compiler recognizes some error, it will let you know through the Compiler window.
You’ll see that the number of errors is not listed as 0, and the word “Error” appears instead of
the word “Success” at the bottom of the window. The errors are to be removed by returning to
the edit window. Usually these errors are a result of a typing mistake. The compiler will not
only tell you what you did wrong; they’ll point you to the exact place in your code where you
made the mistake.
Exiting IDE
An Edit window may be closed in a number of different ways. You can click on the small
square in the upper left corner, you can select close from the window menu, or you can press
the [Alt][F3] combination. To exit from the IDE, select
[Alt][X] Combination.EXERCISEExit from the File Menu or press
1. Type the following program in C Editor and execute it. Mention the Error.
void main(void)
{
printf(“ This is my first program in C ”);
}
2. Add the following line at the beginning of the above program. Recompile the
program. What is the output?
#include<stdio.h>
3. Make the following changes to the program. What Errors are observed?
i. Write Void instead of void .
ii. write void main (void);
iii. Remove the semi colon ‘;’.
iv. Erase any one of brace ‘{’ or ‘}’.
In any language there are certain building blocks:
• Constants
• Variables
• Operators
• Methods to get input from user(scanf( ), getch( ) etc.)
• Methods to display output (Format Specifier, Escape Sequences etc.) etc.
Format Specifiers
Format Specifiers tell the printf statement where to put the text and how to display the text.
The various format specifiers are:
%d => integer
%c => character
%f => float etc.
Variables and Constants
If the value of an item is to be changed in the program then it is a variable. If it will not
change then that item is a constant. The various variable types (also called data type) in C are:
int, float, char, long ,double etc they are also of the type signed or unsigned.
Escape Sequences
Escape Sequence causes the program to escape from the normal interpretation of a string, so
that the next character is recognized as having a special meaning. The back slash “\” character
is called the Escape Character”
\n => new line
\t => tab
\b => back space
\r => carriage return
\” => double quotations
\\ => back slash etc.
. The escape sequence includes the following:
Taking Input From the User
The input from the user can be taken by the following techniques: scanf( ), getch( ), getche( ),
getchar( ) etc.
OperatorsThere are various types of operators that may be placed in three categories:
Basic: + - * / %
Assignment: = += -= *= /= %=
(++, -- may also be considered as assignment operators)
Relational: < > <= >= == !=
Logical: && , || , !
EXERCISE
Program in C to calculate or find aggregate marks and percentage of a student in 5 subject.
1: #include<stdio.h>
2: #include<conio.h>
3: void main()
4: {
5: int m1,m2,m3,m4,m5,aggr;
6: float per;
7: clrscr();
8: printf(“\nEnter marks in 5 subject:”);
9: scanf(“%d%d%d%d%d”,&m1,&m2,&m3,&m4,&m5);
10: aggr=m1+m2+m3+m4+m5;
11: per=aggr/5;
12: printf(“\nAggregate Marks=%d”,aggr);
13: printf(“\nPercentage Marks=%f”,per);
14: printf(“\n\n\n\nPress any key yo exit….”);
15: getch();
16: }
Decision making the if and if-else structure
Normally, your program flows along line by line in the order in which it appears in your
source code. But, it is sometimes required to execute a particular portion of code only if
certain condition is true; or false i.e. you have to make decision in your program. There are
three major decision making structures. The ‘if’ statement, the if-else statement, and the
switch statement. Another less commonly used structure is the conditional operator.
The if statement
The if statement enables you to test for a condition (such as whether two variables are equal)
and branch to different parts of your code, depending on the result or the conditions with
relational and logical operators are also included..
The simplest form of an
if (expression)
statement;
if statement is:
The if-else statement
Often your program will want to take one branch if your condition is true, another if it is false.
If only one statement is to be followed by the if or else condition then there is no need of
parenthesis. The keyword
if (expression)
{ statement/s;
}
else can be used to perform this functionality:
else
{
statement/s;
}
EXERCISE
Decision making the Switch case and conditional operator
Normally, your program flows along line by line in the order in which it appears in your
source code. But, it is sometimes required to execute a particular portion of code only if
certain condition is true; or false i.e. you have to make decision in your program. There are
three major decision making structures. The ‘if’ statement, the if-else statement, and the
switch statement. Another less commonly used structure is the conditional operator.
The switch StatementUnlike if , which evaluates one value, switch statements allow you to branch on any of a
number of different values. There must be break at the end of the statements of each case
otherwise all the preceding cases will be executed including the default condition. The general
form of the switch statement is:
switch (identifier variable)
{
case identifier One: statement;
case identifier Two: statement;
....
case identifier N: statement;
default: statement;
}
Conditional OperatorThe conditional operator ( ?: ) is C’s only ternary operator; that is, it is the only operator to
take three terms.
The conditional operator takes three expressions and returns a value:
(expression1) ? (expression2) : (expression3)
It replaces the following statements of if else structure
If(a>b)
c=a;
else
c=b;
can be replaced by
c=(a>b)?:a:b
This line is read as "If expression1 is true, return the value of expression2; otherwise, return
the value of expression3." Typically, this value would be assigned to a variable.
EXERCISE
Program in C to calculate or find the day on 1st january of any year.
1: #include<stdio.h>
2: #include<conio.h>
3: void main()
4: {
5: int leapdays,firstday,yr;
6: long int normaldays,totaldays;
7: clrscr();
8: printf(“Enter year “);
9: scanf(“%d”,&yr);
10: normaldays=(yr-1)*365L;
11: leapdays=(yr-1)/4-(yr-1)/100+(yr-1)/400;
12: totaldays=normaldays+leapdays;
13: firstday=totaldays%7;
14: if(firstday==0) printf(“\nMonday”);
15: if(firstday==1) printf(“\Tuesday”);
16: if(firstday==2) printf(“\nWednesday”);
17: if(firstday==3) printf(“\nThrusday”);
18: if(firstday==4) printf(“\nFriday”);
19: if(firstday==5) printf(“\nSaturday”);
20: if(firstday==6) printf(“\nSunday”);
21: printf(“\n\n\n\n\nPress any key to exit….”);
22: getch();
23: }
Program in C to calculate profit or loss and by how much?
1: #include<stdio.h>
2: #include<conio.h>
3: void main()
4: {
5: float cp,sp,p,l;
6: clrscr();
7: printf(“Enter cost price and selling price: “);
8: scanf(“%f%f”,&cp,&sp);
9: p=sp-cp;
10: l=cp-sp;
11: if(p>0)
12: printf(“The seller has made a profit of Rs.%f”,p);
13: if(l>0)
14: printf(“The seller is in loss by Rs.%f”,l);
15: if(p==0)
16: printf(“There is no loss or no profit”);
17: printf(“\n\n\n\n\n\nPress any key to exit….”);
18: getch();
19: }
Looping constructs in C-Language
Types of Loops
There are three types of Loops:
1) for Loop
i.for loop
ii.nested for loop
2) while Loop
i.while loop
ii.nested while loop
3) do - while Loop
i.do while loop
ii. nested do while loop
Nesting may extend these loops.
The for Loopfor(initialize(optional);condition(compulsory);increment(optio
nal)
{
Body of the Loop;
}
This loop runs as long as the condition in the center is true. Note that there is no semicolon
after the “for” statement. If there is only one statement in the “for” loop then the braces may
be removed. If we put a semicolon after the for loop instruction then that loop will not work
for any statements.
The while Loop
while(condition is true)
{
Body of the Loop;
}
This loop runs as long as the condition in the parenthesis is true. Note that there is no
semicolon after the “while” statement. If there is only one statement in the “while” loop then
the braces may be re moved.
The do-while Loop
do
{
Body of the Loop;
}
while(condition is true);
This loop runs as long as the condition in the parenthesis is true. Note that there is a
semicolon after the “while” statement. The difference between the “while” and the “do-while”
statements is that in the “while” loop the test condition is evaluated before the loop is
executed, while in the “do” loop the test condition is evaluated after the loop is executed. This
implies that statements in a “do” loop are executed at least once. However, the statements in
the “while” loop are not executed if the condition is not satisfied..
EXERCISE
Program in C to Reverse the given string
//Program to reverse the entered string
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char*str,*str1;
int l,i,k=0;
clrscr();
puts(“Enter a string\n”);
gets(str);
l=strlen(str);
for(i=l-1;i>=0;i–)
{
str1[k]=str[i];
k++;
}
str1[k]=NULL;
printf(“The reverse is %s”,str1);
getch();
}
The Nested for Loop
for(initialize;condition;increment)
{
for(initialize;condition;increment)
{
Body of the loop;
}
}
The inner loop runs as many times as there is the limit of the condition of the external loop.
This loop runs as long as the condition in the parenthesis is true. We can nest many loops
inside as there is the requirement.
The nested while Loopwhile(condition is true)
{
while(condition is true)
{
Body of the loop;
}
Body of the loop;
}
The inner loop runs as many times as there is the limit of the condition of the external loop.
This loop runs as long as the condition in the parenthesis is true. We can nest many loops
inside as there is the requirement.
The Nested do-while Loopdo
{
do
{
body of the loop;
}
while(condition is true);
body of the loop;
}
while(condition is true);
This loop runs as long as the condition in the parenthesis is true. Note that there is a
semicolon after the “while” statement. The difference between the “while” and the “do-while”
statements is that in the “while” loop the test condition is evaluated before the loop is
executed, while in the “do” loop the test condition is evaluated after the loop is executed. This
implies that statements in a “do” loop are executed at least once. The inner loop runs as many
times as there is the limit of the condition of the external loop. This loop runs as long as the
condition in the parenthesis is true. We can nest many loops inside as there is the requirement.
EXERCISE
Program to Print the Pattern:
1
121
12321
1234321
123454321
12345654321
1234567654321
123456787654321
12345678987654321
1: #include<conio.h>
2:
3: #include<stdio.h>
4:
5: void main()
6: {
7: int i, j, k, space, n=9;
8:
9: clrscr();
10: for (i=1; i<=n; i++)
11: {
12: for (j=1; j<=n-i; j++)
13: putchar(' ');
14: for (j=1,k=2*i-1; j<=2*i-1; j++,k--)
15: {
16: if (j <= k)
17: printf("%d", j);
18: else
19: printf("%d", k);
20: }
21: putchar('\n');
22: }
23: getch();
24: }
Debugging and Single-Stepping of C Programs
One of the most innovative and useful features of Turbo C++ is the integration of debugging
facilities into the IDE.
Even if your program compiles perfectly, it still may not work. Such errors that cause the
program to give incorrect results are called Logical Errors. The first thing that should be done
is to review the listing carefully. Often, the mistake will be obvious. But, if it is not, you’ll
need the assistance of the Turbo C Debugger.
One Step at a Time
The first thing that the debugger can do for you is slow down the operation of the program.
One trouble with finding errors is that a typical program executes in a few milliseconds, so all
you can see is its final state. By invoking C++’s single-stepping capability, you can execute
just one line of the program at a time. This way you can follow where the program is going.
Consider the following program:void main(void)
{
int number, answer=-1;
number = -50;
if(number < 100)
if(number > 0)
answer = 1;
else
answer = 0;
printf(“answer is %d\n”, answer);
}
Our intention in this program is that when number is between 0 and 100, answer will be 1,
when the number is 100 or greater, answer will be 0 , and when number is less than 0,
answer will retain its initialized value of –1. When we run this program with a test value of
-50 for number, we find that answer is set to 0 at the end of the program, instead of staying –1
We can understand where the problem is if we single step through the program. To do this,
simply press the [F7] key. The first line of the program will be highlighted. This highlighted
line is called the run bar . Press [F7] again. The run bar will move to the next program line.
The run bar appears on the line about to be executed. You can execute each line of the
program in turn by pressing [F7]. Eventually you’ll reach the first
if (num < 100 )
This statement is true (since number is –50); so, as we would expect the run bar moves to the
second if statement:
if(num>0)
This is false. Because there’s no else matched with the second if, we would expect the run bar
to the printf( ) statement. But it doesn’t! It goes to the line
answer = 0;
Now that we see where the program actually goes, the source of the bug should become clear. The else goes with the last if, not the first if as the indenting would lead us to believe. So, the else is executed when the second need to put braces around the second if statement is false, which leads to erroneous results. We need to put braces around the second if, or rewrite the program in some other way.
Resetting the Debugger
Suppose you’ve single stepped part way through a program, and want to start over at the
beginning. How do you place the run bar at the top of the listing? You can reset the
debugging process and initialize the run bar by selecting the Program Reset option from the
Run menu.
WatchesSingle stepping is usually used with other features of the debugger. The most useful of these
is the watch (or watch expression). This lets you see how the value of variable changes as the
program runs. To add a watch expression, press [Ctrl+F7] and type the expression.BreakpointsIt often happens that you’ve debugged part of your program, but must deal with a bug in
another section, and you don’t want to single-step through all the statements in the first part to
get to the section with the bug. Or you may have a loop with many iterations that would be
tedious to step through. The way to do this is with a breakpoint. A breakpoint marks a
statement where the program will stop. If you start the program with [Ctrl][F9], it will execute
all the statements up to the breakpoint, then stop. You can now examine the state of the
variables at that point using the watch window.
Installing breakpoints
To set a breakpoint, first position the cursor on the appropriate line. Then select Toggle
Breakpoint from the Debug menu (or press [Ctrl][F8]). The line with the breakpoint will be
highlighted. You can install as many breakpoints as you want. This is useful if the program
can take several different paths, depending on the result of if statements or other branching
constructs.
Removing Breakpoints
You can remove a single breakpoint by positioning the cursor on the line with the breakpoint
and selecting Toggle breakpoint from the Debug menu or pressing the [Ctrl][F8] combination
(just as you did to install the breakpoint). The breakpoint highlight will vanish.
You can all set Conditional Breakpoints that would break at the specified value only.
Functions in C-Language programming
Functions are used normally in those programs where some specific work is required to be
done repeatedly and looping fails to do the same.
Three things are necessary while using a function.
i. Declaring a function or prototype:
The general structure of a function declaration is as follows:
return_type function_name(arguments);
Before defining a function, it is required to declare the function i.e. to specify the function
prototype. A function declaration is followed by a semicolon ‘ ;’. Unlike the function
definition only data type are to be me ntioned for arguments in the function declaration.
ii. Calling a function:
The function call is made as follows:
return_type = function_name(arguments);
iii. Defining a function:
All the statements or the operations to be performed by a function are given in the function
definition which is normally given at the end of the program outside the main.
Function is defined as follows
return_type function_name(arguments)
{
Statements;
}
There are certain functions that you have already used e.g: getche( ), clrscr( ), printf( ), scanf( )
etc.
There are four types of functions depending on the return type and arguments:
• Functions that take nothing as argument and return nothing.
• Functions that take arguments but return nothing.
• Functions that do not take arguments but return something.
• Functions that take arguments and return something.
A function that returns nothing must have the return type “void”. If nothing is specified then
the return type is considered as “int”.
Preprocessor Directives
Preprocessor directives are actually the instructions to the compiler itself. They are not
translated but are operated directly by the compiler.
The most common preprocessor directives are
i. include directive
ii. define directive
i. include directive: The include directive is used to include files like as we include header
files in the beginning of the program using #include directive like
#include<stdio.h>
#include<conio.h>
ii. define directive: It is used to assign names to different constants or statements which are
to be used repeatedly in a program. These defined values or statement can be used by main or
in the user defined functions as well.
They are used for
a. defining a constant b.
defining a statement
c. defining a mathematical expression
for example
#define pi 3.142
#define p printf(“enter a new number”);
#define for(a) (4/3.0)*pi*(a*a*a);
They are also termed as macros.
Arrays in C (one dimensional)
An array is a collection of data storage locations, each of which holds the same type of data.
Each storage location is called an element of the array. You declare an array by writing the
type, followed by the array name and the subscript. The subscript is the number of elements in
the array, surrounded by square brackets. For example,
long LongArray[25];
declares an array of 25 long integers, named Long Array. When the compiler sees this
declaration, it sets aside enough memory to hold all 25 elements. Because each long integer
requires 4 bytes, this declaration sets aside 100 contiguous bytes of memory.
Arrays in C (Multidimensional)
A Multidimensional array is a collection of data storage locations, each of which holds the
same type of data. Each storage location is called an element of the array. You declare an
array by writing the type, followed by the array name and the subscript. The subscript is the
number of elements in the array, surrounded by square brackets. For example,
int a[5][10]
declares an array of 50 integers, named a. Its declaration shows that array a comprises of 5
one dimensional arrays and each one dimensional array contains 10 elements.
When the compiler sees this declaration, it sets aside enough memory to hold all 50 elements.
Because each integer requires 2 bytes, this declaration sets aside 100 contiguous bytes of
memory.Learning Text and Graphics modes of display in C
There are two ways to view the display screen in Turbo C graphics model:
• The Text Mode
• The Graphics Mode.
The Text Mode
In the Text Mode, the entire screen is viewed as a grid of cells, usually 25 rows by 80
columns. Each cell can hold a character with certain foreground and background colors (if the
monitor is capable of displaying colors). In text modes, a location on the screen is expressed
in terms of rows and columns with the upper left corner corresponding to (1,1), the column
numbers increasing from left to right and the row numbers increasing vertically downwards.
The Graphics Mode
In the Graphics Mode, the screen is seen as a matrix of pixels, each capable of displaying one
or more color. The Turbo C Graphics coordinate system has its origin at the upper left hand
corner of the physical screen with the x-axis positive to the right and the y-axis positive going
downwards.The ANSI Standard CodesThe ANSI – American National Standards Institute provides a standardized set of codes for
cursor control. For this purpose, a file named ANSI. sys is to be installed each time you turn
on your computer. Using the config.sys file, this job is automated, so that once you’ve got
your system set up, you don’t need to worry about it again.
To automate the loading of ANSI . sys follow these steps:
i. Find the file ANSI.sys in your system. Note the path.
ii. Find the config.sys file. Open this file and type the following:
DEVICE = path_of_ANSI.sys
iii. Restart your computer.
All the ANSI codes start by the character \x1B[ after which, we mention codes specific to
certain operation. Using the #define directive will make the programs easier to write and
understand.
Structures
If we want a group of same data type we use an array. If we want a group of elements of
different data types we use structures. For Example: To store the names, prices and number of
pages of a book you can declare three variables. To store this information for more than one
book three separate arrays may be declared. Another option is to make a structure. No
me mory is allocated when a structure is declared. It simply defines the “form” of the
structure. When a variable is made then memory is allocated. This is equivalent to saying that
there is no memory for “int” , but when we de clare an integer i.e.
is allocated.
The structure for the above mentioned case will look like
Struct books
{char bookname[20];
float price;
int pages;}
struct book[50];
the above structure can hold information of 50 books.
EXERCISE
1. Write a program to maintain the library record for 100 books with book name,
author’s name, and edition, year of publishing and price of the book.
2. Write a program to make a tabulation sheet for a class of 50 students with their names, seat
nos, marks, percentages and grades.
Pointers in C-Language
A pointer provides a way of accessing a variable without referring to the variable
directly. The address of the variable is used.
The declaration of the pointer
int *p;
means that the expression *p is an int. This definition set aside two bytes in which to
store the address of an integer variable and gives this storage space the name p. If
instead of int we declare
char * p;
again, in this case 2 bytes will be occupied, but this time the address stored will b e
pointing to a single byte.
Pointers with arrays and function
A pointer is the most effective tool to pass an array to a function.
If pointers are involved than a function can return more than one values at a time.
We have to pass only the address and size of the array to the function and we can make as
many changes in the function as we want. for example if we want to add 5 in each array
element using functions.
void add(int *,int);
void main(void)
{int s[10],i;
printf(“enter ten integers”);
for(i=0,i<10,i++)
{printf(“\n enter integer no %d :”,i+1);
scanf(“%d”,&s[i]);
}
add(s,10);
for(i=0,i<10,i++)
{printf(“\n integer no %d :%d”,i+1,s[i]);
}
}
void add(int *p,int x)
{int j;
for (j=0;j<x;j++)
{
*p=*p+5;
p++;
}
}
Similarly string arrays and multidimensional arrays can also be passed to functions by
their addresses and size.
1. Write a program to pass an integer array of 10 elements to a function which returns the
same array after sorting it in descending order. Print the array.
Filing in C-Language
Data filesMany applications require that information be “ written & read” fro m an auxiliary
storage device.
This information is written in the form of Data Files .
Data files allow us to store information permanently and to access and alter that
information whenever necessary.
Types of Data filesStandard data files .(stream I/O)
System data files. (low level I/O)
Standard I/O
Easy to work with, & have different ways to handle data.
Four ways of reading & writing data:
1. Character I/O.
2. String I/O.
3. Formatted I/O.
4. Record I/O.
File Protocol
1. fopen
2. fclose
fopen:-
Syntax:It is used to open a file .
fopen (file name , access-mode ).
“r” open a file for reading only.
“w” open a file for writing.
“a” open a file for appending .
“r+” open an existing file for reading & writing.
“w+” open a new file for reading &writing.
“a+” open a file for reading & appending & create a new file if it does exist.
Example:-#include <stdio.h>
main
{
FILE*fpt;
fpt = fopen (“first.txt”,”w”);
fclose(fpt);
}
Establish buffer area, where the information is temporarily stored before being
transferred b/w the computer memory & the data file.
file is a special structure type that establishes the buffer area.
fpt is a pointer variable that indicates the beginning of buffer area.
fpt is called stream pointer.
fopen stands for File Open.
A data file must be opened before it can be created or processed
Standard I/O:
Four way s of reading and writing data:
Character I/O.
String I/O.
Formatted I/O.
Record I/O.
Character I/O:
In normal C program we used to use getch, getchar and getche etc.
In filling we use putc and getc.
putc( );
It is used to write each character to the data file.
Putc requires specification of the stream pointer *fpt as an argument.
Syntax:putc(c, fp);
c = character to be written in the file .
fp = file pointer .
putch or putchar writes the I/P character to the consol while putc writes to the file.
Example (1):Reading the Data File:#include < stdio.h >
main( )
{
FILE*fpt;
Char c;
fpt = fopen ( “ star.dat”,”r”);
if( fpt = = NULL);
printf( “Error- cant open”);
else
do
putchar(c=getc(fpt) );
while(c!=‘\n’ );
fclose( fpt );
}
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