Static Local Data in C
#include <stdio.h>
/*
* This example demonstrates a simple use of static data. It also makes some
* more advanced use of printf. The program prints a very simple ledger. The
* function print_line keeps a running balance, printing one line each time it
* is called. It uses static data to keep track of the total, and to condition
* the first call to print headers. The use of static is important, since
* the value of the first flag and of the balance must persist between calls
* to print_line.
*/
/*
* Print table line. It receives a description and an amount.
*/
void print_line(char *descr, double amt)
{
static int first = 1; /* Identifies first call. */
static double balance = 0.0; /* Running balance. */
/* First time through, print header line. */
if(first)
{
printf("%-20s%10s%10s\n", "Description", "Amount", "Balance");
printf("%-20s%10s%10.2f\n", "Initial Balance", "", 0.0);
first = 0;
}
/* Now, process the transaction, and print. */
balance += amt;
printf("%-20s%10.2f%10.2f\n", descr, amt, balance);
}
/* Just a convenient place to keep pairs of test data arguments for
print_line. */
struct legdat
{
char *descr;
double amt;
};
/*
* Just a boring test driver
*/
main()
{
/* Lists of data to send to the ledger. */
struct legdat legdat[] = {
"Paycheck", 1579.17,
"Gas", -14.56,
"Rent", -550.16,
"Refund", 33.45,
"Pizza Party", -155.18,
"New Carpet", -250.00,
NULL };
struct legdat *scan;
/* Go through the data and print the lines. */
for(scan = legdat; scan->descr != NULL; ++scan)
print_line(scan->descr, scan->amt);
}
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