How to write functions that use values from other functions

Question

I am a complete beginner at c so please give me advice that is as simple as possible. I have two questions. How do you use scanf in a function with pointers because my program is not working at all. Also, how do you write functions that uses values from another function. For example I have to write a function that asks for employee name, hours worked, and hourly rate. And then I have to write another function that uses that information to calculate gross pay and overtime pay. This is the scanf code I wrote so far:

#include <stdio.h>
     #include <stdlib.h>
     int employeedata(char *ch, float *x, float *y)
      {
      printf("Enter your name:\n");
       scanf_s("%s", &ch);
      printf("Enter your hourly rate:\n");
      scanf_s("%f", &x);
       printf("Enter number of hours worked:\n");
       //variables
           scanf_s("%f", &y);
      }
  int main() {

           float rate[5], hours[5];
       float overtimerate = 1.5;
       char name[5][20];

           int loop;

           //loop 5 times
           for (loop = 0; loop < 5; loop++)
           {
            //call function
                employeedata(name[loop], &rate[loop], &hours[loop]);
           //use if to break out of loop after input if -1 is entered
                if (strcmp(name, "-1") == 0)
                 break;

                if (rate[loop] == -1)
                 break;

               if (hours[loop] == -1)
                 break;
            }
        system("pause");
        return 0;

}

Turn up your compiler warnings to pedantic levels. The warnings you get should be very telling. — WhozCraig
– WhozCraig, Commented Jul 23, 2016 at 8:51

Madhusoodan P · Accepted Answer · 2016-07-23 09:00:53Z

1

You are passing pointer to a pointer in scanf function in line

scanf_s("%s", &ch);

But scanf requires pointers to buckets where you want the read values to be put. Hence the corrected code should be

scanf_s("%s", ch);

Same error in lines

 scanf_s("%f", &x);
 scanf_s("%f", &y);

which must be

 scanf_s("%f", x);
 scanf_s("%f", y);

Because x, y & ch themselves are pointers

More: Here is the prototype for the scanf()

int scanf(const char *format_string, ...);

where "..." (ellipsis) refer to pointers to the buckets.

answered Jul 23, 2016 at 9:00

Madhusoodan P

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t.elazari · Accepted Answer · 2016-07-23 10:05:43Z

edit: here is an example for everything you wanted

#include <stdio.h>
#include <stdlib.h>

char *inputString(FILE* fp, size_t size) {
    //The size is extended by the input with the value of the provisional
    char *str;
    int ch;
    size_t len = 0;
    str = realloc(NULL, sizeof(char)*size);//size is start size
    if (!str)return str;
    while (EOF != (ch = fgetc(fp)) && ch != '\n') {
        str[len++] = ch;
        if (len == size) {
            str = realloc(str, sizeof(char)*(size += 16));
            if (!str)return str;
        }
    }
    str[len++] = '\0';
    return realloc(str, sizeof(char)*len);
}


void CalcFunc(double hours, double rate, double* gross, double* otime);





int main(void) {
    char *name;
    double HoursWorked = 0, RatePerHour = 0, GroosPay =0, OverTime=0;
    printf("input name: ");
    name = inputString(stdin, 10);


    printf("input hours worked: ");
    scanf("%lf", &HoursWorked);

    printf("input rate per hour: ");
    scanf("%lf", &RatePerHour);

    CalcFunc(HoursWorked, RatePerHour, &GroosPay, &OverTime);
    printf("Name:%s\n", name);
    printf("hours worked:%.2f\n", HoursWorked);
    printf("rate per hour:%.2f\n", RatePerHour);
    printf("over time:%.2f\n", OverTime);
    printf("gross pay:%.2f\n", GroosPay);

    free(name);
    return 0;
}



void CalcFunc(double hours, double rate, double* gross, double* otime) {
//just an example for function
    *otime = hours*2;
    *gross = hours*rate*0.3;
    return;
}

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