#ifdef

Starts a conditional assembly block, making assembly conditional on the definition of a symbol.

  #ifdef symbol statement-group

Parameters

symbol

Any valid symbol.

statement-group

Any valid assembly statements.

Remarks

If previous code includes a definition for symbol, the preprocessor implements the statements of the block. If symbol is not defined, the preprocessor skips the statements of the block.

Each #ifdef directive must have a matching #endif directive.