C header file 'stdlib' functions implementation

#include<stdio.h>
#include<stdlib.h>
//code by rajendra
main(){
    int ival,d_plc,sign;
    long lval;
    unsigned long ulval=362880L;
    float real1,real2=-57.12345;
    char str1[20]="-250",str2[20]="765.2345",str3[20],str4[33],*str5;
    ival=atoi(str1);
    lval=atol("12345678");
    real1=atof(str2);
    printf("%d %ld %.4f\n",ival,lval,real1);
    itoa(67,str3,8);
    ultoa(ulval,str4,2);
    printf("%s %s\n", str3,str4);
    str5=fcvt(real2,5,&d_plc,&sign);
    printf("%.5f conversion gives: String %s,Decimal is at place %d, Sign is %d",real2,str5,d_plc,sign);
  
}