APPENDIX D: DISPLAY ORDERS GENERATED BY FOG ROUTINES

The VT15 hardware orders generated by FOG append-type are described here. The subroutines are listed in Appendix A; the same argument identifiers are used here. The display orders are described in terms of symbolic names which are defined first. The numbers are octal.

Symbolic names

PY    = 140000     / POSITION, Y DIRECTION
PX    = 144000     / POSITION, X DIRECTION
SVY   = 100000     / STROKE VECTOR, Y DIRECTION
SVX   = 104000     / STROKE VECTOR, X DIRECTION
DJMS  = 640000     / display JMS
DJMP  = 600000     / display jump
CHAR  = 0          / single character instruction
SC    = 20         / scale enable
INT   = 2000       / intensity enable
LP    = 10         / lightpen enable
BK    = 1000       / BLINK enable
DSH   = 4          / dash enable
OFST  = 2          / offset enable
ROTAT = 40         / rotate enable
LODN  = 400        / load name register enable
PRM1  = 200000     / parameter word 1 op code
PRM2  = 210000     / parameter word 2 op code
PRM3  = 220000     / parameter word 3 op code
SKP2  = 234000     / SKIP2 op code
SYNC  = 236000     / SYNC order
SAVE  = 240000     / SAVE instruction
RSTR  = 260000     / RESTORE instruction

D.1 Picture parameter routines

One display order is generated for each routine

BLINK (I)    PRM2 + BK + (400 + I) 
BRITE (I)    PRM1 + INT + (200 * I) 
DASH  (I)    PRM3 + DSH + I 
LPVIS (I)    PRM2 + LP + (4 * I) 
OFFST (I)    SKP2 + lodn + i 
NAME  (I)    PRM2 + OFST + I 
ROT   (I)    PRM2 + ROTAT + (20 * I) 
SCALE (I)    PRM2 + SC + I

D.2 Image-creating routines

(a) DRAW (I,IARRAY(I))

if I=0 (occupies 3 words)

DJMP  .+2
S
DJMS+ .-1

if I=1 (occupies 6 words)

DJMP .+3 
S
Save/restore word 
SAVE .-1 
DJMS* .-3 
RSTR .-3

where S Is the address of the subpicture, ie, the address of the array element IARRAY (I+1).

(b) LINE (I,J,K)

The orders generated depend on the size and direction of (I,J) and also on the flag QLLARB (which can be set with the routine ALLARB) which determines whether only arbitrary vectors are to be used (if so QLLARB is .TRUE.)

1. if I = J = 0: no display orders are produced
2. if (I = 0 or J = 0 or IABS(I) = IABS(J)) and (QLLARB = .FALSE.): then 1 basic vector is used
3. if not (i) or (ii) and (IABS(I)< 32₁₀ ) and (IABS(J)<32₁₀ ): then 1 arbitrary short vector is used
4. if not (i) or (ii) or (iii) then 2 long arbitrary vector orders.

(c) SETPT (I,J,K)

1. if I < 0 and J < 0: no display orders
2. if I < 0 ≤ J: one display order ie PY + (20000 * K)+J
3. if J < 0 ≤ I: one display order ie PX + (20000 * K)+I
4. if 0 ≤I and 0 ≤ J: two display order PX +I, PY + (20000 * K)+J

(d) SYMB (I)

One display order: CHAR + I

(e) TEXT (T,J)

Three locations are required:

DJMP .+2 
address of T 
CHARS* .-1