A Simple C Program
Every
C program must have one special function main (). This is the point where
execution begins when the program is running. We will see later that this does
not have to be the first statement in the program, but it must exist as the
entry point. The group of statements defining the main () enclosed
in a pair of braces ({}) are executed sequentially. Each expression statement
must end with a semicolon. The closing brace of the main function signals
the end of the program. The main function can be located anywhere in the
program but the general practice is to place it as the first function.
Here is an elementary C program.
main ()
{
}
There
is no way to simplify this program, or to leave anything out. Unluckily, the
program does not do anything. Following the "main" program name is a
couple of parentheses, which are an indication to the compiler that this is a
function. The 2 curly brackets { }, properly called braces, are used to specify
the limits of the program itself. The actual program statements go between the
2 braces and in this case, there are no statements because the program does
absolutely nothing. You will be able to compile and run this program, but since
it has no executable statements, it does nothing. Keep in mind however, that it
is a legal C program.
main
( ) function should return zero or one. Turbo C accepts both int and void main
( ) and Turbo C coders use both int and void main ( ) in their programs. But in
my belief, void main ( ) is not a standard usage. The reason is, whenever a
program gets executed it returns an integer to the OS. If it returns 'zero',
the program is executed successfully. Otherwise it means the program has been
ended with error. So main ( ) shouldn't be declared as void.d as void.
main( ) should be
declared as
int main( )
{
……………..
……………..
return 0 ;
}
.For a much more interesting program, load the program
int
main ()
{
printf (“Welcome to C
language”);
return 0;
}
and display it on your
monitor. It is same as the previous program except that it has one
executable statement between the
braces.
The executable statement is another function. Again, we won't care
about what a function is, but only how to use this one. In order to output text
to the monitor, it's placed within the function parentheses and bounded by
quotes. The end result is that whatever is included between the quotes will be
showed on the monitor when the program is run.
Notice
the semi-colon; at the end of the line. C uses a semi-colon as a statement
terminator, so semi-colon is required as a signal to the compiler that this
line is complete. This program is also executable, so you'll be able to compile
and run it to see if it does what you think it should. With some compilers, you
may get an error message while compiling, indicating that the function printf
() should have a prototype.
#include<stdio.h>
#include<conio.h>
int
main ()
{
printf
(“Welcome to C language”);
return 0;
}
}
Here
you'll be able to see #include at the beginning of the program. It is a
pre-processor directive. It's not a part of our program; it's an instruction to
the compiler to make it do something. It says the C compiler to include the
contents of a file, in this case the system file stdio.h. This is the name of
the standard library definition file for all Standard Input Output. Your
program will almost certainly want to send stuff to the screen and read things
from the keyboard. stdio.h is the name of the file in which the functions that
we want to use are defined. A function is simply a group of related
statements that we can use later. Here the function we used is printf .
To use printf correctly C needs to know what it looks like, i.e. what things it
can work on and what value it returns. The actual code which performs the
printf will be tied in later by the linker. Note that without the definition of
what printf looks like the compiler makes a guess when it sees the use of it.
This can lead to the call failing when the program runs, a common cause of
programs crashing.
The
<> characters around the name tell C to look in the system area for the
file stdio.h. If I had given the name "abc.h" instead it would
tell the compiler to look in the current directory. This means that I can
arrange libraries of my own routines and use them in my programs.
Imagine
you run above program and then change it and run it again you may find that the
previous output is still stucked there itself, at this time clrscr(); would
clear the previous screen.
One more thing to remember while using clrscr() is that it should be called only after the variable declaration, like
One more thing to remember while using clrscr() is that it should be called only after the variable declaration, like
int p,q,r;
clrscr()
Here is an example of
minimal C program that displays the string Welcome to C language (this famous
example included in all languages moreover been
done originally in C in 1978 from the creators of the language, Brian Kernighan
and Dennis Ritchie) there are many Example at the end of the page:
#include<stdio.h>
#include<conio.h>
#include<conio.h>
int main ()
{
clrscr();
printf (“Welcome to C
language”);
return 0;
}
When
you execute above program you won’t see ‘Welcome to C language’ on
the console because the screen will just flash and go away
.If you want to see the line you can use getch() function just below the
printf() statement. Actually it waits until a key is pressed.
Example:
c programming examples
Click here to see more examples
===========
1.
1.
main()
{
}
========================
2.
void main()
{
}
========================
3.
int main()
{
return 0;
}
========================
4.
int main ()
{
printf ("Welcome to C language");
return 0;
}
========================
5.
#include <stdio.h>
#include <conio.h>
int main ()
{
clrscr();
printf (“Welcome to C language”);
return 0;
}
========================
6.
#include <stdio.h>
#include <conio.h>
int main ()
{
clrscr();
printf (“Welcome to C language”);
getch();
retun 0;
}
========================
String: strlen()
#include <stdio.h>
#include <conio.h>
int main()
{
char str[30]="C PROGRAMMING Muhammad Shoaib Khan";
clrscr();
printf("\n\nstr : %s\n\n",str);
printf("\nLength of the string, strlen(str) is %d\n",strlen(str));
getch();
return 0;
}
========================
String: strlwr()
#include <stdio.h>
#include <conio.h>
int main()
{
char str[30]="C PROGRAMMING";
clrscr();
printf("\n\nstr : %s\n\n",str);
printf("strlwr(str) : %s\n",strlwr(str));
getch();
return 0;
}
========================
String: strupr()
#include <stdio.h>
#include <conio.h>
int main()
{
char str[30]="C Programming Muhammad Shoaib Khan";
clrscr();
printf("\n\nstr : %s\n\n",str);
printf("strupr(str) : %s\n",strupr(str));
getch();
return 0;
}
========================
String: strcat()
#include <stdio.h>
#include <conio.h>
int main()
{
char str1[25]="I LIKE ";
char str2[15]="C PROGRAMMIG Muhammad Shoaib Khan";
clrscr();
printf("\n\nstr1 : %s\t\t\tstr2 : %s\n\n",str1,str2);
printf("\n\nstrcat(str1,str2) : %s\n\n",strcat(str1,str2));
printf("\n\nstr1 : %s\t\tstr2 : %s\n\n",str1,str2);
getch();
return 0;
}
========================
String: strncat()
#include <stdio.h>
#include <conio.h>
int main()
{
char str1[25]="I LIKE ";
char str2[13]="C PROGRAMMIG Muhammad Shoaib Khan";
clrscr();
printf("\n\nBEFORE:\n\nstr1 : %s\t\t\tstr2 : %s\n\n",str1,str2);
printf("\n\nstrncat(str1,str2,5) : %s\n\n",strncat(str1,str2,5));
printf("\n\nAFTER:\n\nstr1 : %s\t\tstr2 : %s\n\n",str1,str2);
getch();
return 0;
}
========================
String: strcpy()
#include <stdio.h>
#include <conio.h>
int main()
{
char str1[15]="I LIKE ";
char str2[15]="C PROGRAMMIG Muhammad Shoaib Khan";
clrscr();
printf("\n\nBEFORE:\n\nstr1 : %s\t\t\tstr2 : %s\n\n",str1,str2);
strcpy(str1,str2);
printf("\n\nAFTER:\n\nstr1 : %s\t\tstr2 : %s\n\n",str1,str2);
getch();
return 0;
}
========================
String: strncpy()
#include <stdio.h>
#include <conio.h>
int main()
{
char str1[25]="I LIKE ";
char str2[15]="C PROGRAMMIG Muhammad Shoaib Khan";
clrscr();
printf("\n\nBEFORE:\n\nstr1 : %s\t\t\tstr2 : %s\n\n",str1,str2);
strncpy(str1,str2,4);
printf("\n\nAFTER:\n\nstr1 : %s\t\tstr2 : %s\n\n",str1,str2);
getch();
return 0;
}
========================
String: strcmp()
#include <stdio.h>
#include <conio.h>
int main()
{
char str1[]="I LIKE";
char str2[]="C Expert Muhammad Shoaib Khan";
int i;
clrscr();
i=strcmp(str1,str2);
if(i==0)
printf("\n\nstr1 and str2 are identical");
else if(i<0)
printf("\n\nstr1< str2");
else
printf("\n\nstr1< str2");
getch();
return 0;
}
========================
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