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15.561 Information Technology
Essentials
Thomas Malone
Acknowledgments: Slides marked “SM” are adapted from Stuart Madnick, MIT.
MEMORY • There are 100 “locations” on the blackboard • Each location identified by number from 00 to 99 • Each location has room for one 3-digit number • Load moves number from blackboard to register. Example: LOAD 01 • Store moves number from register to blackboard. Example: STORE 00
SM
PROCESSOR MEMORYINPUT/OUTPUT
IN
OUT
+030 +400 7 4 1 0
8
2 5
+
9 6
-3
421 00 01 02 03
98 97 … 05 04
99
602 311 006 007 212 134
BLACKBOARD CALCULATORPUT
GET REGISTER
INPUT/OUTPUT • Input and Output conveyors hold 3-digit numbers • GET moves number from INPUT to REGISTER • PUT moves number from REGISTER to OUTPUT
SM
PROCESSOR MEMORYINPUT/OUTPUT
IN
OUT
+030 +400 7 4 1 0
8
2 5
+
9 6
-3
421 00 01 02 03
98 97 … 05 04
99
602 311 006 007 212 134
BLACKBOARD CALCULATOR
REGISTER
PROCESSOR/CALCULATOR • Register has room for one 3-digit number • Calculator can add and subtract numbers from memory to
registerExamples: ADD 02
SMSUBTRACT 03
LMC INSTRUCTIONS
PROCESSORPROCESSOR MEMORYMEMORYINPUT/OUTPUT
IN
OUT
+030 +400 7 4 1 0
8
2 5
+
9 6
-3
421 00 01 02 03
98 97 … 05 04
99
602 311 006 007 212 134
BLACKBOARD CALCULATOR
INPUT/OUTPUT
REGISTERGET
PUT
ADD
STORE
SUB
LOAD
1. Get 2. Put 3. Load x (Load 01) 4. Store x (Store 05) 5. Add x (Add 02) 6. Sub x (Sub 03) 7. Stop
SM
SYMBOLIC LMC ADDRESSES
PROCESSORPROCESSOR MEMORYMEMORYINPUT/OUTPUT
IN
OUT
+030 +400 7 4 1 0
8
2 5
+
9 6
-3
CALCULATOR
INPUT/OUTPUT
REGISTER 00
98 97 96
99
596
400 030 000 006
WAGE BONUS PAY
Label Loc Contents
EXAMPLE INSTRUCTION SEQUENCE Optional 2-digit 3-digit number number
Program 0. Get 1. Store 20 2. Add 19 3. Put 4. Stop
MEMORY
REGISTER
ISSUES: • Where is LMC program stored? • How does LMC understand instructions like STOP? It only likes numbers. • How does LMC handle symbolic labels like A, B, C? ANSWERS (Stored Program Concept):
SM •
LMC MACHINE LANGUAGE AND ASSEMBLY LANGUAGEPROCESSOR MEMORY
op-code symbolic 000 stop 1xx add 2xx subtract 3xx store 5xx load 901 get 902 put
STEP INSTRUCTION 00 get01 store w 02 get03 store b 04 load w 05 06 07 stop