3. Steps to write C programs on Terminal
• Open terminal : Press Ctrl+Alt+T: Ubuntu/Linux terminal
shortcut
• On shell prompt type as below:
$gedit filename.c
•This will start the gedit text editor.
• In editor type your program, save it and close editor.
4. Steps to write C programs on Terminal
• On shell prompt type:
gcc –o filename filename.c
• gcc, normally does preprocessing, compilation, assembly and
linking.
• This will create object file.
gcc -o writes the build output to an output file.
• Now type : ./filename for execution
5. Program 1: To find average of two numbers
#include <stdio.h>
int main()
{
int number1, number2;
float res;
printf("Enter the First Number to find = ");
scanf("%d",&number1);
printf("Enter the Second Number to find = ");
scanf("%d",&number2);
int sm = number1 + number2;
res = sm/2; //(float)sum/2;
printf("The Sum of %d and %d = %dn", number1, number2, sm);
printf("The Average of %d and %d = %.2fn", number1, number2, res);
return 0;
}
6. Program 1: To find average of two numbers
Steps to run C program on Ubuntu
student@AUHDT0766:~$ gedit add1.c
student@AUHDT0766:~$ gcc -o add1 add1.c
student@AUHDT0766:~$ ./add1
Enter the First Number to find = 23
Enter the Second Number to find = 45
The Sum of 23 and 45 = 68
The Average of 23 and 45 = 34.00
student@AUHDT0766:~$
7. Program 2: To find Volume of a Cube
#include<stdio.h>
void main()
{//start the program
int h,w,d,vol;//variables declaration
h=10;w=12;d=8;//assign value to variables
vol=h*w*d;//calculation usingmathematical formula
printf("The Volume of the cube is: %d",vol);//display the volume
return ;
//end the main program
}
8. Program 2: : To find Volume of a Cube
student@AUHDT0766:~$ gedit first.c
student@AUHDT0766:~$ gcc -o first first.c
student@AUHDT0766:~$ ./first
The Volume of the cube is: 960
9. Program 3: Program to Print Sum of all Even
Numbers from 1 to N
#include<stdio.h>
int main()
{
int i, number, Sum = 0;
printf("n Please Enter the Maximum Limit Value : ");
scanf("%d", &number);
printf("n Even Numbers between 0 and %d are : ", number);
for(i = 1; i <= number; i++)
{
if ( i%2 == 0 ) //Check whether remainder is 0 or not
{
printf("%d ", i);
Sum = Sum + i;
}
}
printf("n The Sum of All Even Numbers upto %d = %d", number, Sum);
return 0;
}
10. Program 3: Program to Print Sum of all Even
Numbers from 1 to N
student@AUHDT0766:~$ gedit second.c
student@AUHDT0766:~$ gcc -o second second.c
student@AUHDT0766:~$ ./second
Please Enter the Maximum Limit Value : 67
Even Numbers between 0 and 67 are : 2 4 6 8 10 12 14 16 18 20
22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60
62 64 66
The Sum of All Even Numbers upto 67 = 1122
11. Program 4: Program to Reverse a Number
using a while loop
#include <stdio.h>
int main()
{
int Number, Reminder, Reverse = 0;
printf("nPlease Enter any number to Reversen");
scanf("%d", & Number);
while (Number > 0)
{
Reminder = Number %10;
Reverse = Reverse *10+ Reminder;
Number = Number /10;
}
printf("Reverse of entered number is = %dn", Reverse);
return 0;
}
12. Program 4: Program to Reverse a Number
using a while loop
student@AUHDT0766:~$ gedit rev.c
student@AUHDT0766:~$ gcc -o rev rev.c
student@AUHDT0766:~$ ./rev
Please Enter any number to Reverse
78
Reverse of entered number is = 87
student@AUHDT0766:~$ ./rev
Please Enter any number to Reverse
678459
Reverse of entered number is = 954876
13. Program 5: Program to add two numbers using
function
#include<stdio.h>
int add (int x, int y);
int main() {
int a, b, result;
printf("Enter First Number");
scanf("%d",&a);
printf("Enter Second Number");
scanf("%d",&b);
result = add(a, b);
printf("%d + %d = %dn", a, b, result);
return 0; }
int add (int x, int y) {
x += y;
return(x);
}
14. Program 5: Program to add two numbers using
function
student@AUHDT0766:~$ gedit fadd.c
student@AUHDT0766:~$ gcc -o fadd fadd.c
student@AUHDT0766:~$ ./fadd
Enter First Number45
Enter Second Number23
45 + 23 = 68
15. Program 6: Factorial of a Number Using
Recursion
#include<stdio.h>
long int multiplyNumbers(int n);
int main() {
int n;
printf("Enter a positive integer: ");
scanf("%d",&n);
printf("Factorial of %d = %ld", n, multiplyNumbers(n));
return 0;
}
long int multiplyNumbers(int n) {
if (n>=1)
return n*multiplyNumbers(n-1);
else
return 1;
}
16. Program 6: Factorial of a Number Using
Recursion
student@AUHDT0766:~$ gedit fact.c
student@AUHDT0766:~$ gcc -o fact fact.c
student@AUHDT0766:~$ ./fact
Enter a positive integer: 8
Factorial of 8 = 40320
17. Fork System Call in C
•Fork system call is used for creating a new process, which is
called child process.
•It runs concurrently with the process that makes the fork() call
(parent process).
•After a new child process is created, both processes will
execute the next instruction following the fork() system call.
•A child process uses the same pc(program counter), same CPU
registers, same open files which use in the parent process.
19. Fork System Call in C
fork() takes no parameters and returns an integer value.
Below are different values returned by fork().
•Negative Value: creation of a child process was unsuccessful.
•Zero: Returned to the newly created child process.
•Positive value: Returned to parent or caller.
The value contains process ID of newly created child process.
The syntax of the fork() system function is as follows:
pid_t fork(void);
20. Fork System Call in C
The fork() system function does not accept any
argument. It returns an integer of the type pid_t.
The pid_t data type represents process IDs.
You can get the process ID of a process by calling getpid.
On success, fork() returns the PID of the child process
which is greater than 0. Inside the child process, the
return value is 0. If fork() fails, then it returns -1.
21. Important Header Files
sys/types.h: Defines data types used in system source
code.
They can be used to enhance portability across different
machines and operating systems.
unistd.h: Defines miscellaneous symbolic constants and
types, and declares miscellaneous functions like version
constant etc.
sys/wait.h: declarations for waiting
22. Fork System Call in C
//Predict the Output of the following program:.
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
int main()
{
// make two process which run same
// program after this instruction
fork();
printf("Hello world!n");
return 0;
}
23. Fork System Call in C
Output:
student@AUHDT0766:~$ gedit forksys.c
student@AUHDT0766:~$ gcc -o forksys forksys.c
student@AUHDT0766:~$ ./forksys
Hello world!
Hello world!
The number of times ‘hello’ is printed is equal to
number of process created. Total Number of Processes
= 2n, where n is number of fork system calls.
Hence, 21=2 in above program.
24. PROGRAM FOR SYSTEM CALLS OF UNIX OPERATING
SYSTEM (fork, getpid, exit)
ALGORITHM:
STEP 1: Start the program.
STEP 2: Declare the variables pid,pid1,pid2.
STEP 3: Call fork() system call to create process.
STEP 4: If pid==-1, exit.
STEP 5: Ifpid!=-1 , get the process id using getpid().
STEP 6: Print the process id.
STEP 7:Stop the program
25. PROGRAM FOR SYSTEM CALLS OF UNIX OPERATING
SYSTEM (fork, getpid, exit)
#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
int main()
{
int pid,pid1,pid2;
pid=fork();
if(pid==-1)
{
printf("error in process creation");
exit(1);
}
26. PROGRAM FOR SYSTEM CALLS OF UNIX OPERATING
SYSTEM (fork, getpid, exit)
if(pid==0)
{
pid1=getpid();
printf("n the parent process id is %dn",pid1);
}
else
{
pid2=getpid();
printf("n the child process ID is %dn",pid2);
}
}
27. PROGRAM FOR SYSTEM CALLS OF UNIX OPERATING
SYSTEM (fork, getpid, exit)
student@AUHDT0766:~$ gedit fork2.c
student@AUHDT0766:~$ gcc -o fork2 fork2.c
student@AUHDT0766:~$ ./fork2
the child process ID is 4005
the parent process id is 4006
28. PROGRAM FOR SYSTEM CALLS OF UNIX
OPERATING SYSTEMS (OPENDIR, READDIR,
CLOSEDIR)
ALGORITHM:
STEP 1: Start the program.
STEP 2: Create Struct dirent.
STEP 3: declare the variable buff and pointer dptr.
STEP 4: Get the directory name.
STEP 5:Open the directory.
STEP 6: Read the contents in directory and print it.
STEP 7: Close the directory.
29. PROGRAM FOR SYSTEM CALLS OF UNIX
OPERATING SYSTEMS (OPENDIR, READDIR,
CLOSEDIR)
Data Type: struct dirent
This is a structure type used to return information about directory
entries.
It contains directory/file name, file serial number, length etc.
30. PROGRAM FOR SYSTEM CALLS OF UNIX OPERATING
SYSTEMS (OPENDIR, READDIR, CLOSEDIR)
#include<stdio.h>
#include<dirent.h>
#include<stdlib.h>
struct dirent *dptr;
int main()
{
char buff[100];
DIR *dirp;
printf("enter dir name");
scanf("%s", buff);
31. PROGRAM FOR SYSTEM CALLS OF UNIX OPERATING
SYSTEMS (OPENDIR, READDIR, CLOSEDIR)
if((dirp=opendir(buff))==NULL)
{
printf("the given directory does not exist.");
exit(1);
}
while(dptr=readdir(dirp))
{
printf("%sn",dptr->d_name);
}
closedir(dirp);
}
}
}
32. PROGRAM FOR SYSTEM CALLS OF UNIX OPERATING
SYSTEMS (OPENDIR, READDIR, CLOSEDIR)
Before running the above program you must have some directory
with further subdirectories and files in it. If you already use that
directory else create new as given below.
student@AUHDT0766:~$ mkdir ch
student@AUHDT0766:~$ cd ch
student@AUHDT0766:~/ch$ ls
student@AUHDT0766:~/ch$ mkdir dir1 dir2 dir3
tudent@AUHDT0766:~/ch$ ls
dir1 dir2 dir3
student@AUHDT0766:~/ch$ cat > file1
Hello Everyone.
student@AUHDT0766:~/ch$ cd ..
33. PROGRAM FOR SYSTEM CALLS OF UNIX OPERATING
SYSTEMS (OPENDIR, READDIR, CLOSEDIR)
Running the Program:
student@AUHDT0766:~$ gedit dir1.c
student@AUHDT0766:~$ gcc -o dir1 dir1.c
Output:
student@AUHDT0766:~$ ./dir1
enter dir name ch
dir1
dir2
.
file1
..
dir3
student@AUHDT0766:~$ ./dir1
enter dir name
nn
the given directory does not exist.
