Never define main as void return. Start defining main as int main( void ) or int main ( int argc, char *argv[] ) if you are expecting arguments from the command line.

>Sorry i never learn about <ctype.h>, isalpha, islower and isupper, is there other way???

C Syntax (Toggle Plain Text)

#include <stdio.h>
/* #define ALL_CHARACTER */ /* enable for use all characters in RANGE */
/* #define RANGE */  /* enable for only lower case */
#ifdef RANGE
#define START 'a'
#endif
#ifndef RANGE
#define START 'A'
#endif
 
int main( void )
{     
    char character[256] = { 0 };
    int c = '\0';
 
    puts( "Enter some text:" );
 
    while ( ( c = getchar() ) != '\n' && c != EOF )
    {
        ++character[c];
    }
    for ( c = START; c <= 'z'; c++ )
    {
#ifndef ALL_CHARACTER
        if ( character[c] )
#endif
            printf( "%c = %d\n", c, character[c] );
    }
    getchar();
    return 0;
}

#include <stdio.h> /* #define ALL_CHARACTER */ /* enable for use all characters in RANGE */ /* #define RANGE */ /* enable for only lower case */ #ifdef RANGE #define START 'a' #endif #ifndef RANGE #define START 'A' #endif int main( void ) { char character[256] = { 0 }; int c = '\0'; puts( "Enter some text:" ); while ( ( c = getchar() ) != '\n' && c != EOF ) { ++character[c]; } for ( c = START; c <= 'z'; c++ ) { #ifndef ALL_CHARACTER if ( character[c] ) #endif printf( "%c = %d\n", c, character[c] ); } getchar(); return 0; }

Cannot you use std::string apis ?

Aiks, i really fresh in C. Your coding contain some element i never learn before.

i copy paste the code and run it, it work perfectly.

Cannot you use std::string apis ?
>i never learn about it. haha