C51: Variable Zero Initialization

Information in this article applies to:

• C51, all versions
• CX51, all versions
• C251, all versions

QUESTION

The C51 User's Guide states that the file INIT.A51 initializes variables that were explicitly initialized in the 'C' source.

Does it also initialize variables that are implicitly initialized to zero, or does it rely on the zeroing of memory in STARTUP.A51 to do this?

Is there a difference in the following two statements, or are they identical?

static int xdata xi;

static int xdata xi = 0;

ANSWER

Yes, the compiler relies on the zero initialization in the STARTUP file. For strict ANSI compliance, it is important that the settings match with your hardware.

When you make explicit assignments such as:

static int xdata xi = 0;

the variables get set to zero by the INIT.A51 file. This behavior allows you to use non-volatile memory for variables.

MORE INFORMATION

• Refer to Variable Initialization Code in the Cx51 User's Guide.

SEE ALSO

• C51: Battery-backed Non-volatile Memory
• C51: Mixing SRAM and NVRAM

Last Reviewed: Thursday, February 25, 2021