BYTE

SUNDB86x Only

The BYTE compiler directive allows the insertion of 8-bit values that represent machine code instructions within PL/B source code. These values perform instructions normally unavailable in PL/B. The instruction uses one of the following formats:

(1)	[label]	BYTE	{code}
(2)	[label]	BYTE	{code}:
			{code}:
			...etc

Where:

label

Optional. A Program Execution Label.

code

Required. One or more control literals (binary, decimal, hex, or octal) containing 8 bit absolute machine code, Data Definition Labels, a VARLIST of valid Data Definition Labels that are inserted into the PL/B object code.

Flags Affected: NONE

Note the following:

The value of each item in {code} is not translated but written into the output code exactly as given. This instruction should only be used by programmers knowledgeable in machine language. This is an area where Sunbelt may offer examples but will not provide support, except at prevailing time and material consulting rates.
Multiple {code} items may be placed on a single line and may be continued onto other lines using the colon (:) line continuation technique.
A Data Definition Label may be a {code} item that references a variable. The compiler automatically inserts the address of the variable, in correct byte order, in place of the referenced variable.
Multiple +/- operations may be performed on an address by placing a plus (+) or minus (-) sign and a valid Ctrl literal designating the number of offset bytes immediately following the Data Definition Label.
When referencing variables within {code}, care should be taken not to overwrite the variable designator or Form Pointer/Length Pointer (as appropriate). When a Data Definition Label is used, the memory location referenced is not the first byte of the data for the variable. Therefore, it is necessary to increment this address by one for FORMs or INTEGERs and by two for DIMs or INITs to access the data therein.
Moving data into a DIM/INIT does not automatically adjust the Form Pointer or Length Pointer as if performed through other PL/B instructions. Any data transferred may not be accessible until the Form Pointer and Length Pointer have been adjusted appropriately.
If the DS, ES, SS, or SP registers are modified, they must be saved prior to such modification and restored before executing a PL/B instruction other than BYTE or WORD. The saving and restoration may be accomplished using BYTE/WORD instructions.

Example 1:

*
.Print the screen on the default printer.
.
	BYTE	0xCD,0x5	INT 5 ; MS-DOS Print Screen

Example 2:

*
.Determine total configured memory in bytes.
.
TEMP	INTEGER	2
MEMORY	FORM	6
	BYTE	0x3E,0x8D,0x3E,TEMP+1:
		0xCD,0x12:
		0x3E,0x89,0x5
	MULT	"1024",TEMP,MEMORY

Load Effective Address of TEMP's data area (TEMP+1) into DS:DI.
INT 12 returns number of 1k blocks of configured memory in AX (in INTEGER format).
MOVe the integer value returned in AX to TEMP (pointed to by DS:DI).
MULTiply TEMP by "1024" placing the result in MEMORY.

Example 3:

*
.Turn on the NUM Lock on a PC.
.
	BYTE	0x1E	PUSH DS
	BYTE	0xB8,0x40,0x0	MOV AX,40H
	BYTE	0x8E,0xD8	MOV DS,AX
	BYTE	0x80,0xE,0x17,0x0,0x20
.			OR DS:Byte Ptr[17h],20h
	BYTE	0x1F	POP DS

Save the contents of the DS register.
Move 40h into AX register.
Move the contents of the AX register to the DS register.
Bitwise ORs the value of 20H into the value located at DS:[17h].
Restores the contents of the DS register..

See Also: BYTEX, ENTERZ/EXITZ, WORD, WORDX, and Compiler Directives