C calculator program doesnt work properly

Question

I wrote a calculator program in C but it doesnt work as intended. P is an acumulator that stores the current number, its like a memory of calculator. if you want to perform an operation, like +, you do P + , it doesnt matter if + or numbers are on different lines, blank spaces dont count. My code works for P 20 + 20 as intended. If you want to get the result you type =. So if You input P 20 + 20 = , the result should be 40. For P 20 + 20 + 20 the result should be 60, however, in my program its still 40. I will attach photos of my inputs and the expected inputs.

Code:

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

void print_error_message(char *message)
{
    fprintf(stderr, "%s\n", message);
}


bool calculate(void)
{
    int ch;
    int akumulator = 0;
    int number = 0;
    char operation = 0;
    while ((ch = getchar()) != EOF)
    {
        if (ch == '\n' || ch == ' ') {
            continue;
        }

        switch(ch)
        {
            case 'P':
                operation = 1;
                akumulator = 0;
                break;
            case '+':
                number = 0;
                operation = 2;
                break;

            default:
                ;
        }

        if (operation == 1)
        {
            if (isdigit(ch)){
                akumulator = (akumulator *  10) + (ch - '0');
            }
        }

        if (operation == 2)
        {
            if (isdigit(ch)){
                number = (number *  10) + (ch - '0');
            } else{
                akumulator = akumulator + number;
            }
        }

        if ((operation == 0) && isdigit(ch))
        {
            print_error_message("Syntax error");
            return false;
        }

        if (operation != 0)
        {
            if (ch == '=' || ch == ';' || ch == '+')
            {
                printf("# %d", akumulator);
                putchar('\n');
            }
            if (ch == EOF)
            {
                printf("# %d", akumulator);
                putchar('\n');
            }
        }

        if (ch == '=')
        {
            printf("# %d", akumulator);
            putchar('\n');
        }

    }
    print_error_message("SYNTAX ERROR");

    return false;
}


int main(void)
{
    if (!calculate()) {
        return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;

}

Answer 1

Reset the number only after incrementing it in the accumulator. See the below code (commented the modified parts):

while ((ch = getchar()) != EOF)
{
    if (ch == '\n' || ch == ' ') {
        continue;
    }

    switch(ch)
    {
        case 'P':
            operation = 1;
            akumulator = 0;
            break;
        case '+':
            //removed the number reset
            operation = 2;
            break;

        default:
            ;
    }

    if (operation == 1)
    {
        if (isdigit(ch)){
            akumulator = (akumulator *  10) + (ch - '0');
        }
    }

    if (operation == 2)
    {
        if (isdigit(ch)){
            number = (number *  10) + (ch - '0');
        } else{
            akumulator = akumulator + number;
            number = 0; // number is resetted here!
        }
    }

    if ((operation == 0) && isdigit(ch))
    {
        print_error_message("Syntax error");
        return false;
    }

    if (operation != 0)
    {
        if (ch == '=' || ch == ';' || ch == '+')
        {
            printf("# %d", akumulator);
            putchar('\n');
        }
        if (ch == EOF)
        {
            printf("# %d", akumulator);
            putchar('\n');
        }
    }

    if (ch == '=')
    {
        printf("# %d", akumulator);
        putchar('\n');
    }

}