#include<string.h>
#include<ctype.h>
#include<stdio.h>
#include<stdlib.h>
void keyword(char str[10])
{
 if(strcmp("for",str)==0||strcmp("while",str)==0||strcmp("do",str)==0||strcmp("int",str)==0||strcmp("float",str)==0||strcmp("char",str)==0||strcmp("double",str)==0||strcmp("printf",str)==0||strcmp("switch",str)==0||strcmp("case",str)==0)
  printf("\n%s is a keyword",str);
 else
  printf("\n%s is an identifier",str);
}
void main()
{
 FILE *f1,*f2,*f3;
 char c,str[10],st1[10];
 int num[100],lineno=0,tokenvalue=0,i=0,j=0,k=0;
 f1=fopen("input","r");
 f2=fopen("identifier","w");
 f3=fopen("specialchar","w");
 while((c=getc(f1))!=EOF)
 {
  if(isdigit(c))
  {
  tokenvalue=c-'0';
  c=getc(f1);
  while(isdigit(c))
  {
   tokenvalue*=10+c-'0';
   c=getc(f1);
  }
  num[i++]=tokenvalue;
  ungetc(c,f1);
  }
  else
  if(isalpha(c))
  {
   putc(c,f2);
   c=getc(f1);
   while(isdigit(c)||isalpha(c)||c=='_'||c=='$')
   {
    putc(c,f2);
    c=getc(f1);
   }
   putc(' ',f2);
   ungetc(c,f1);
  }
  else
  if(c==' '||c=='\t')
  printf(" ");
  else
  if(c=='\n')
  lineno++;
  else
  putc(c,f3);
 }
 fclose(f2);
 fclose(f3);
 fclose(f1);
 printf("\n the no's in the program are:");
 for(j=0;j<i;j++)
  printf("\t%d",num[j]);
 printf("\n");
 f2=fopen("identifier","r");
 k=0;
 printf("the keywords and identifier are:");
 while((c=getc(f2))!=EOF)
 if(c!=' ')
 str[k++]=c;
 else
 {
  str[k]='\0';
  keyword(str);
  k=0;
 }
 fclose(f2);
 f3=fopen("specialchar","r");
 printf("\n Special Characters are");
 while((c=getc(f3))!=EOF)
 printf("\t%c",c);
 printf("\n");
 fclose(f3);
 printf("Total no of lines are:%d",lineno);
}

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
}