#include <stdio.h>
#include <string.h>

int main () {

   char str1[20] = "Happy";
   char str2[20] = "learning";
   char str3[20];
   char str4[20] = "learning";
   char str[50] = "Hello world, learning is fun.";

   int  length, cmp , cmp1 ;
   int *ptr, * ptr1;  
   
   length = strlen(str1); // to find length of a string
   printf("length of string is :  %d\n", length );
   
   strcat( str1, str2); // concatenates str1 and str2 
   printf("Concatenation of str1 and str2:   %s\n", str1 );

   strcpy(str3, str1); // to copy a string into another
   printf("string copy of str1 to str3 :  %s\n", str3 );

   cmp = strcmp(str2,str4); // to compare two strings
   printf("string compare result :  %d\n", cmp );
   
   
   cmp1 = strcmp(str1,str4); // to compare two strings
   printf("string compare result :  %d\n", cmp1 );
   
   ptr = strchr(str1, 'p'); // usage of strchr
   printf("pointer to the first occurrence of p in string Happy :  %d\n", ptr );
   
   ptr1 = strstr(str, str2); // usage of strstr
   printf("pointer to the first occurrence of str2 in str :  %d\n", ptr1 );
   

   return 0;
}
by

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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
}