Initializing 10 bytes to zero

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Byte

Joined: 21 Mar 2026
Posts: 33

Byte 13 Sep 2026, 10:41

Why does the string

Code:

_PBCD_res       dt   0

cause an error?

Code:

flat assembler  version 1.73.35  (1048576 kilobytes memory)
bosvars.asm [32]:
processed: _PBCD_res dt 0
error: invalid operand

And the next line

Code:

_PBCD_res       dt   ?

doesn't get on an error?

13 Sep 2026, 10:41

bitRAKE

Joined: 21 Jul 2003
Posts: 4614
Location: vpcmpistri

bitRAKE 13 Sep 2026, 11:04

From the manual ...

Quote:

dt accepts the word and quad word value separated with colon, the quad word is stored first. The dt directive with single expression as parameter accepts only floating point values and creates data in FPU double extended precision format.

... it covers two data types, and the question mark means to reserve space for.

13 Sep 2026, 11:04

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 21108
Location: In your JS exploiting you and your system

revolution 13 Sep 2026, 12:31

More specifically, to place zero do this:

Code:

_PBCD_res       dt   0:0

Or this:

Code:

_PBCD_res       dt   0.0

13 Sep 2026, 12:31

Byte

Joined: 21 Mar 2026
Posts: 33

Byte 13 Sep 2026, 14:19

Thanks, everyone.
But it’s strange—zero should be zero everywhere, regardless of whether it’s an integer or a floating-point number.

13 Sep 2026, 14:19

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 21108
Location: In your JS exploiting you and your system

revolution 13 Sep 2026, 14:42

There isn't any 10 byte integer format in x86. It is segment¹(16)+offset(64).

There is a 10 byte FP format in x86.

¹aka selector

13 Sep 2026, 14:42

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