// Write a program that takes a string, and displays the first 'a' character it
// encounters in it, followed by a newline. If there are no 'a' characters in the
// string, the program diplays 'a' followed by a newline. If the number of parameters is not
// 1, the program displays 'a' followed by a newline.

// Example:

// $> ./aff_a "abc" | cat -e
// a$
// $> ./aff_a 'RaInB0w d4Sh!' | cat -e
// a$
// $> ./aff_a 'ThE C4k3 Is a L|3' | cat -e
// a$
// $> ./aff_a | cat -e
// a$
// z2t12c2:aff_a exam$ 
#include <stdio.h>
#include <unistd.h>
// int main(int argc, char *argv[])
// {
//   (void)argc;
//   (void)**argv;
//   write(1, "a\n", 2);
//   return (0);
// }
// Write a function that print a string but in reverse order.
// It must return its parameter.
// Beware that the string wont be modifiable.
// Your function must be declared as follows:

// char    *rev_print(char *str);

// Examples:

// intmain(void)
// {
// rev_print("rainbow dash");
// write(1, "\n", 1);
// rev_print("Ponies are awesome");
// write(1, "\n", 1);
// rev_print("");
// write(1, "\n", 1);
// return (0);
// }

// $> ./a.out | cat -e
// hsad wobniar$
// emosewa era seinoP$
// $
// $>
// z2t12c2:rev_print exam$ 
// int count_lenght(char *str)
// {
//   int i;
  
//   i = 0;
//   while(str[i] != '\0')
//     i++;
//   return (i);
// }

// char  *rev_print(char *str)
// {
//   int i;
//   int n;
//   char temp;
  
//   i = 0;
//   n = count_lenght(str);
//   if (i < n)
//   {
//   while(str[i] != '\0' && str[n] != '\t')
//     {
//       str[i] = str[n-1];
//     }
//     // str[size] = *temp;
//     i++;
//     n--;
//     return (&str);
//   }
//   str[i] = '\0';
//   return (0);
// }

// int main(void)
// {
//   // int result;
//   char t;
//   // char s[] = "rainbow dash";
  
//   // result = rev_print("rainbow dash"); 
//   // printf("result is%d", result);
//   // t = rev_print(s);
//   // printf("%s", t);
//   t = rev_print("raiw dash");
//   printf("%s", t);
//   write(1, "\n", 1);
//   rev_print("Ponies are awesome");
//   write(1, "\n", 1);
//   rev_print("");
//   write(1, "\n", 1);
//   return (0);
// }

int count_lenght(char *str)
{
  int len;
  
  len = 0;
  while(str[len] != '\0')
    len++;
  return (len);
}

char  *rev_print(char *str)
{
  int i;
  int n;
  char tab[n];
  
  i = 0;
  n = count_lenght(str);
  n--;
  while(i < n)
  {
    tab[n] = str[i] ;
    i++;
  return (&tab[n]);
  }
}

int main(void)
{
  char result;
  
  result = *rev_print("rainbow diw");
  printf("rever %s", result);
  
}

C Language online compiler

Write, Run & Share C Language code online using OneCompiler's C online compiler for free. It's one of the robust, feature-rich online compilers for C language, running the latest C version which is C18. Getting started with the OneCompiler's C editor is really simple and pretty fast. The editor shows sample boilerplate code when you choose language as 'C' and start coding!

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
}