C语言不同的存储类型

// parta.c --- various storage classes
// compile with partb.c
#include <stdio.h>
void report_count();
void accumulate(int k);
int count = 0;       // file scope, external linkage

int main(void)
{
    int value;       // automatic variable
    register int i;  // register variable

    printf("Enter a positive integer (0 to quit): ");
    while (scanf("%d", &value) == 1 && value > 0)
    {
        ++count;     // use file scope variable
        for (i = value; i >= 0; i--)
            accumulate(i);
        printf("Enter a positive integer (0 to quit): ");
    }
    report_count();

    return 0;
}

void report_count()
{
    printf("Loop executed %d times\n", count);
}

// partb.c -- rest of the program
// compile with parta.c
#include <stdio.h>

extern int count;       // reference declaration, external linkage

static int total = 0;   // static definition, internal linkage
void accumulate(int k); // prototype

void accumulate(int k)  // k has block scope, no linkage
{
    static int subtotal = 0;  // static, no linkage

    if (k <= 0)
    {
        printf("loop cycle: %d\n", count);
        printf("subtotal: %d; total: %d\n", subtotal, total);
        subtotal = 0;
    }
    else
    {
        subtotal += k;
        total += k;
    }
}