A variable with an initial value is normally transferred from a ROM area to a RAM area at startup, and processing is performed using the RAM area. Accordingly, if the value is initialized data which is unchangeable in the program, the allocated RAM area goes to waste. If the const operator is added to initialized data, transfer to the RAM area at startup is disabled and the amount of used memory can be saved.

In addition, writing a program based on the rule of not changing the initial values also makes usage of ROM easier.

[Example before improvement]

char a[] = { 1, 2, 3, 4, 5 };

Initial values are transferred from ROM to RAM and then processing is performed.

[Example after improvement]

const char a[] = { 1, 2, 3, 4, 5 };

Processing is performed using the initial values in ROM.