Menu
I have this code here, but I'm unfamiliar with the syntax.
STACK16_SIZE = 100h
stack16 db STACK16_SIZE dup (?)
I think dup means we declare a variable of type array, as this is a stack, but I'm not sure. So what does dup mean in TASM, exactly?
705
The DUP directive tells the assembler to duplicate an expression a given number of times. For example, 4 DUP(2) is equivalent to 2, 2, 2, 2.
The DUP operator is very often used in the declaration of arrays This operator works with any of the data allocation directives. the count value sets the number of times to repeat all values within the parentheses.
"dw" is variable of type WORD, "db" is variable of type BYTE, dd is variable of type double word (int32_t). "?" means the values are not initialized.
Asking for help, clarification, or responding to other answers.
STACK16_SIZE dup (?) means to duplicate the data in parenthesis by STACK16_SIZE times. It is equivalent to writing ?, ?, ?, ?, ... (100h times)
The data in parens is "uninitialized data". That is, memory is allocated, but not set to any particular value on load.
Assembly does not provide an array "type". If it does, it is only for debuggers for use when inspecting the data. However, in this code snippet, stack16 is a symbol with an address beginning a memory block of bytes—which is counter-intuitive and potentially a source of a subtle bug. For a CPU stack, it really ought to be defined as 16 bit words (dw) or 32 bit words (dd).
115
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
