Phase -1 MULTIPROGRAMMING OPERATING SYSTEM (MOS) PROJECT
First Version
ASSUMPTIONS:
• Jobs entered without error in input file
• No physical separation between jobs
• Job outputs separated in output file by 2 blank lines
• Program loaded in memory starting at location 00
• No multiprogramming, load and run one program at a time
• SI interrupt for service request
NOTATION
M: memory; IR: Instruction Register (4 bytes)
IR [1, 2]: Bytes 1, 2 of IR/Operation Code
IR [3, 4]: Bytes 3, 4 of IR/Operand Address
M[&]: Content of memory location &
IC: Instruction Counter Register (2 bytes)
R: General Purpose Register (4 bytes)
C: Toggle (1 byte)
: Loaded/stored/placed into
MOS (MASTER MODE)
SI = 3 (Initialization)
Case SI of
1: Read
2: Write
3: Terminate
Endcase
READ
IR [4] 0
Read next (data) card from input file in memory locations IR [3,4] through IR [3,4] +9
If M [IR [3,4]] = $END, abort (out-of-data)
EXECUTEUSERPROGRAM
WRITE
IR [4] 0
Write one block (10 words of memory) from memory locations IR [3,4] through IR [3,4] + 9 to
output file
EXECUTEUSERPROGRAM
TERMINATE
Write 2 blank lines in output file
MOS/LOAD
2
LOAD
m 0
While not e-o-f
Read next (program or control) card from input file in a buffer
Control card: $AMJ, end-while
$DTA, MOS/STARTEXECUTION
$END, end-while
Program Card: If m = 100, abort (memory exceeded)
Store buffer in memory locations m through m + 9
m m + 10
End-While
STOP
MOS/STARTEXECUTION
IC 00
EXECUTEUSERPROGRAM
EXECUTEUSERPROGRAM (SLAVE MODE)
Loop
IR M [IC]
IC IC+1
Examine IR[1,2]
LR: R M [IR[3,4]]
SR: R → M [IR[3,4]]
CR: Compare R and M [IR[3,4]]
If equal C T else C F
BT: If C = T then IC IR [3,4]
GD: SI = 1
PD: SI = 2
H: SI = 3
End-Examine
End-Loop
Phase 2 - MULTIPROGRAMMING OPERATING SYSTEM (MOS) PROJECT
Second Phase
ASSUMPTIONS:
Jobs may have program errors
PI interrupt for program errors introduced
No physical separation between jobs
Job outputs separated in output file by 2 blank lines
Paging introduced, page table stored in real memory
Program pages allocated one of 30 memory block using random number generator
Load and run one program at a time
Time limit, line limit, out-of-data errors introduced
TI interrupt for time-out error introduced
2-line messages printed at termination
NOTATION
M: memory
IR: Instruction Register (4 bytes)
IR [1, 2]: Bytes 1, 2 of IR/Operation Code
IR [3, 4]: Bytes 3, 4 of IR/Operand Address
M[&]: Content of memory location &
IC: Instruction Counter Register (2 bytes)
R: General Purpose Register (4 bytes)
C: Toggle (1 byte)
PTR: Page Table Register (4 bytes)
PCB: Process Control Block (data structure)
VA: Virtual Address
RA: Real Address
TTC: Total Time Counter
LLC: Line Limit Counter
TTL: Total Time Limit
TLL: Total Line Limit
EM: Error Message
: Loaded/stored/placed into
INTERRUPT VALUES
SI = 1 on GD
= 2 on PD
= 3 on H
TI = 2 on Time Limit Exceeded
PI = 1 Operation Error
= 2 Operand Error
= 3 Page Fault
Error Message Coding
2
EM Error
0 No Error
1 Out of Data
2 Line Limit Exceeded
3 Time Limit Exceeded
4 Operation Code Error
5 Operand Error
6 Invalid Page Fault
BEGIN
INITIALIZATION
SI = 3, TI = 0
MOS (MASTER MODE)
Case TI and SI of
TI SI Action
0 1 READ
0 2 WRITE
0 3 TERMINATE (0)
2 1 TERMINATE (3)
2 2 WRITE, THEN TERMINATE (3)
2 3 TERMINATE (0)
Case TI and PI of
TI PI Action
0 1 TERMINATE (4)
0 2 TERMINATE (5)
0 3 If Page Fault Valid, ALLOCATE, update page Table, Adjust IC if necessary,
EXECUTE USER PROGRAM OTHERWISE TERMINATE (6)
2 1 TERMINATE (3,4)
2 2 TERMINATE (3,5)
2 3 TERMINATE (3)
READ
If next data card is $END, TERMINATE (1)
Read next (data) card from input file in memory locations RA through RA + 9
EXECUTEUSERPROGRAM
WRITE
LLC LLC + 1
If LLC > TLL, TERMINATE (2)
Write one block of memory from locations RA through RA + 9 to output file
EXECUTEUSERPROGRAM
TERMINATE (EM)
Write 2 blank lines in output file
Write 2 lines of appropriate Terminating Message as indicated by EM
LOAD
LOAD
3
While not e-o-f
Read next (program or control) card from input file in a buffer
Control card: $AMJ, create and initialize PCB
ALLOCATE (Get Frame for Page Table)
Initialize Page Table and PTR
Endwhile
$DTA, STARTEXECUTION
$END, end-while
Program Card: ALLOCATE (Get Frame for Program Page)
Update Page Table
Load Program Page in Allocated Frame
End-While
End-While
STOP
STARTEXECUTION
IC 00
EXECUTEUSERPROGRAM
END (MOS)
EXECUTEUSERPROGRAM (SLAVE MODE)
ADDRESS MAP (VA, RA)
Accepts VA, either computes & returns RA or sets PI 2 (Operand Error) or PI 3 (Page Fault)
LOOP
ADDRESSMAP (IC, RA)
If PI ≠ 0, End-LOOP (F)
IR M[RA]
IC IC+1
ADDRESSMAP (IR[3,4], RA)
If PI ≠ 0, End-LOOP (E)
Examine IR[1,2]
LR: R M [RA]
SR: R M [RA]
CR: Compare R and M [RA]
If equal C T else C F
BT: If C = T then IC IR [3,4]
GD: SI = 1 (Input Request)
PD: SI = 2 (Output Request)
H: SI = 3 (Terminate Request)
Otherwise PI 1 (Operation Error)
End-Examine
End-LOOP (X) X = F (Fetch) or E (Execute)
SIMULATION
Increment TTC
If TTC = TTL then TI 2
If SI or PI or TI ≠ 0 then Master Mode, Else Slave Mode