Macro Constants

Object-like macros name compile-time constants before the compiler sees the program.

object-like macro The preprocessor replaces a macro name with its replacement text before parsing.

runtime use The trace uses the expanded value so the replay stays aligned with source lines.

                            price
                            price = 20 (default)price = 15price = 30
                        

                            macro_constants.c
                        
Replay: real traced execution (multi-file project)

                            #include <stdio.h>

#define TAX_RATE 8

int main(void) {
    int price = 20;
    int taxRate = 8;
    int tax = price * taxRate / 100;
    int total = price + tax;

    printf("total=%d\n", total);
    return 0;
}
#include <stdio.h>

#define TAX_RATE 8

int main(void) {
    int price = 15;
    int taxRate = 8;
    int tax = price * taxRate / 100;
    int total = price + tax;

    printf("total=%d\n", total);
    return 0;
}
#include <stdio.h>

#define TAX_RATE 8

int main(void) {
    int price = 30;
    int taxRate = 8;
    int tax = price * taxRate / 100;
    int total = price + tax;

    printf("total=%d\n", total);
    return 0;
}

                        
1price ← 20, taxRate ← 8, tax ← 1, total ← 21⋯5int main(void) {6    int price→ 20 = 20; //@price=15, 307    int taxRate→ 8 = 8;8    int tax→ 1 = price20 * taxRate8 / 100;9    int total→ 21 = price20 + tax1;1011    printf("total=%d\n", total21);12    return 0;13}⋯outputtotal=21
1price ← 15, taxRate ← 8, tax ← 1, total ← 16⋯5int main(void) {6    int price→ 15 = 15;7    int taxRate→ 8 = 8;8    int tax→ 1 = price15 * taxRate8 / 100;9    int total→ 16 = price15 + tax1;1011    printf("total=%d\n", total16);12    return 0;13}⋯outputtotal=16
1price ← 30, taxRate ← 8, tax ← 2, total ← 32⋯5int main(void) {6    int price→ 30 = 30;7    int taxRate→ 8 = 8;8    int tax→ 2 = price30 * taxRate8 / 100;9    int total→ 32 = price30 + tax2;1011    printf("total=%d\n", total32);12    return 0;13}⋯outputtotal=32