#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h>
void string_copy(char d[],char s[])
{
int i;
for(i = 0; s[i]!='\0'; i++)
d[i] = s[i];
d[i] = '\0';
}
void substring(char d[], char s[], int pos, int len)
{
int i;
for(i = 0; i < len; i++)
d[i] = s[pos - 1 + i];
d[i] = '\0';
}
void string_concat(char d[],char s[])
{
int i, len;
len = string_length(d);
for(i = 0; s[i] != '\0'; i++)
{
d[len+i] = s[i];
}
d[len+i] = '\0';
}
int string_length(char s[])
{
int i, length = 0;
for(i = 0; s[i] !='\0'; i++)
length++;
return(length);
}
void string_reverse(char s[])
{
int i, j;
char temp; 
Computer Programming and Numerical Methods 21
for(i = 0, j = string_length(s)-1; i < j; i++, j--)
{
temp = s[i];
s[i] = s[j];
s[j] = temp;
}
}
main()
{
int len, pos, choice, a;
char s[50], d[50];
clrscr();
printf("\n Welcome to storing functions \n");
printf("\n 1. Copy \n 2. Substring \n 3. Concatenation \n
 4. Reverse \n 5. Length \n 6. Exit \n");
do
{
printf("Enter your choice :");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("\n Enter the string :");
scanf("%s",s);
string_copy(d,s);
printf("\n The copied string is %s \n",d);
break;
case 2:
printf("\n Enter the string :");
scanf("%s",s);
printf("\n Enter the starting position and length of string
\n");
scanf("%d %d",&pos,&len);
substring(d,s,pos,len);
printf("\n The substring is %s \n",d);
break;
case 3:
printf("\n Enter the string :");
scanf("%s %s",d,s);
string_concat(d,s);
printf("\n The string is %s \n",d);
break;
case 4:
printf("\n Enter the string :");
scanf("%s",s); 
Computer Programming and Numerical Methods 22
string_reverse(s);
printf("\n The reverse of the string is %s \n",s);
break;
case 5:
printf("\n Enter the string :");
scanf("%s",s);
a = string_length(s);
printf("\n The length of the string is %d \n",a);
break;
case 6: exit(0);
default:printf("\n Invalid choice \n");
}
}while(choice != 7);
return 0;
}
by

C Language online compiler

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Read inputs from stdin

OneCompiler's C online editor supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample C program which takes name as input and print your name with hello.

#include <stdio.h>
int main()
{
    char name[50];
    printf("Enter name:");
    scanf("%s", name);
    printf("Hello %s \n" , name );
    return 0;
    
}

About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}