Figure 2.1. Binary, signed-integer representations.

Figure 2.1. Binary, signed-integer representations.
V alues represented Sign and b b b b magnitude 1' s complement 2' s complement 3 2 1 1 1 1 + 7 + 7 + 7 1 1 + 6 + 6 + 6 1 1 + 5 + 5 + 5 1 + 4 + 4 + 4 1 1 + 3 + 3 + 3 1 + 2 + 2 + 2 1 + 1 + 1 + 1 + + + 1 - - 7 - 8 1 1 - 1 - 6 - 7 1 1 - 2 - 5 - 6 1 1 1 - 3 - 4 - 5 1 1 - 4 - 3 - 4 1 1 1 - 5 - 2 - 3 1 1 1 - 6 - 1 - 2 1 1 1 1 - 7 - - 1 Figure Binary, signed-integer representations.

Figure 2.2. Addition of 1-bit numbers.
1 1 + + + 1 + 1 1 1 1 Carry-out Figure 2.2. Addition of 1-bit numbers.

Please see “portrait orientation” PowerPoint file for Chapter 2
Figure 2.3. Modular number systems and the 2's-complement system.

Figure 's-complement Add and Subtract operations.

Figure 2.5. Memory words.

• for positive numbers for negative numbers
32 bits • b b b b 31 30 1 Sign bit: b = for positive numbers 31 b = 1 for negative numbers 31 (a) A signed integer 8 bits 8 bits 8 bits 8 bits ASCII ASCII ASCII ASCII character character character character (b) Four characters Figure 2.6. Examples of encoded information in a 32-bit word.

• • Figure 2.7. Byte and word addressing. W ord address Byte address
1 2 3 3 2 1 4 4 5 6 7 4 7 6 5 4 • • k k k k k k k k k k 2 - 4 2 - 4 2 - 3 2 - 2 2 - 1 2 - 4 2 - 1 2 - 2 2 - 3 2 - 4 (a) Big-endian assignment (b) Little-endian assignment Figure Byte and word addressing.

Figure A program for C ¬ [A] + [B].

Figure A straight-line program for adding n numbers.

Figure Using a loop to add n numbers.

Figure 2.11. Indirect addressing.
Add (R1),R0 Add (A),R0 Main memory B Operand A B R1 B Register B Operand (a) Through a general-purpose register (b) Through a memory location Figure Indirect addressing.

Figure 2.12. Use of indirect addressing in the program of Figure 2.10.
Contents Move N,R1 Move #NUM1,R2 Initialization Clear R0 LOOP Add (R2),R0 Add #4,R2 Decrement R1 Branch>0 LOOP Move R0,SUM Figure Use of indirect addressing in the program of Figure 2.10.

Figure Indexed addressing.

Figure A list of students' marks.

Move #LIST,R0 Clear R1 Clear R2 Clear R3 Move N,R4 LOOP Add 4(R0),R1 Add 8(R0),R2 A d d 12(R0),R3 Add #16,R0 Decrement R4 Branch>0 LOOP Move R1,SUM1 Move R2,SUM2 Move R3,SUM3 Figure Indexed addressing used in accessing test scores in the list in Figure 2.14.

Move N,R1 Move #NUM1,R2 Initialization Clear R0 LOOP Add (R2)+,R0 Decrement R1 Branch>0 LOOP Move R0,SUM Figure The Autoincrement addressing mode used in the program of Figure 2.12.

Figure Memory arrangement for the program in Figure 2.12.

Memory Addressing address or data lab el Op eration information Assem bler directiv es SUM EQU 200 ORIGIN 204 N D A T A W ORD 100 NUM1 RESER VE 400 ORIGIN 100 Statemen ts that ST AR T MO VE N,R1 generate MO VE #NUM1,R2 mac hine CLR R0 instructions LOOP ADD (R2),R0 ADD #4,R2 DEC R1 BGTZ LOOP MO VE R0,SUM Assem bler directiv es RETURN END ST AR T Figure Assembly language representation for the program in Figure 2.17.

Mo v e #LOC,R0 Initialize p oin ter register R0 to p oin t to the address of the first lo cation in memory where the c haracters are to b e stored. READ T estBit #3,INST A TUS W ait for a c haracter to b e en tered Branc h=0 READ in the k eyb oard buffer D A T AIN. Mo v eByte D A T AIN,(R0) T ransfer the c haracter from D A T AIN in to the memory (this clears SIN to 0). ECHO T estBit #3,OUTST A TUS W ait for the displa y to b ecome ready . Branc h=0 ECHO Mo v eByte (R0),D A T A OUT Mo v e the c haracter just read to the displa y buffer register (this clears SOUT to 0). Compare #CR,(R0)+ Chec k if the c haracter just read is CR (carriage return). If it is not CR, then Branc h 0 READ branc h bac k and read another c haracter. Also, incremen t the p oin ter to store the next c haracter. Figure A program that reads a line of characters and displays it.

Figure A stack of words in the memory.

Figure Effect of stack operations on the stack in Figure 2.21.

SAFEPOP Compare #2000,SP Chec k to see if the stac k p oin ter con
tains Branc h > EMPTYERR OR an address v alue greater than 2000. If it do es, the stac k is empt y . Branc h to the routine EMPTYERR OR for appropriate action. Mo v e (SP)+,ITEM Otherwise, p op the top of the stac k in to memory lo cation ITEM. (a) Routine for a safe pop operation SAFEPUSH Compare #1500,SP Chec k to see if the stac k p oin ter Branc  h FULLERR OR con tains an address v alue equal to or less than 1500. If it do es, the stac k is full. Branc h to the routine FULLERR OR for appropriate action. Mo v e NEWITEM, – (SP) Otherwise, push the elemen t in memory lo cation NEWITEM on to the stac k. (b) Routine for a safe push operation Figure Checking for empty and full errors in pop and push operations.

Figure Subroutine linkage using a link register.

Calling program Mo v e N,R1 R1 serv es as a coun ter. Mo v e #NUM1,R2 R2 p oints to the list. Call LIST ADD Call subroutine. Mo v e R0,SUM Sa v e result. . . . Subroutine LIST ADD Clear R0 Initialize sum to 0. LOOP Add (R2)+,R0 Add en try from list. Decremen t R1 Branc h > LOOP Return Return to calling program. Figure Program of Figure 2.16 written as a subroutine; parameters passed through registers.

Figure Program of Figure 2.16 written as a subroutine; parameters passed on the stack.

Figure A subroutine stack frame example.

Figure Nested subroutines.

Figure Stack frames for Figure 2.28.

Figure Logical and arithmetic shift instructions.

Mo v e #LOC,R0 R0 points to data. Mo v eByte (R0)+,R1 Load first b yte in to R1. LShiftL #4,R1 Shift left b y 4 bit p ositions. Mo v eByte (R0),R2 Load second b yte in to R2. And #$F,R2 Eliminate high-order bits. Or R1,R2 Concatenate the BCD digits. Mo v eByte R2,PACKED Store the result. Figure A routine that packs two BCD digits.

Figure Rotate instructions.

Figure 2.33. A program for computing the dot product of two vectors.
Mo v e #A VEC,R1 R1 p oin ts to v ector A. Mo v e #BVEC,R2 R2 p oin ts to v ector B. Mo v e N,R3 R3 serv es as a coun ter. Clear R0 R0 accum ulates the dot pro duct. LOOP Mo v e (R1)+,R4 Compute the pro duct of Multiply (R2)+,R4 next comp onen ts. Add R4,R0 Add to previous sum. Decremen t R3 Decremen t the coun ter. Branc h > LOOP Loop again if not done. Mo v e R0,DOTPR OD Store dot pro duct in memory . Figure A program for computing the dot product of two vectors.

Figure A byte-sorting program using a straight-selection sort.

Figure 2.35. Linked-list data structure.
Link address Record 1 Record 2 Record k Head T ail (a) Linking structure Record 1 Record 2 Ne w record (b) Inserting a new record between Record 1 and Record 2 Figure Linked-list data structure.

Figure A list of student test scores organized as a linked list in memory.

Figure A subroutine for inserting a new record into a linked list.

Figure 2.38. A subroutine for deleting a record from a linked list.
DELETION Compare (RHEAD), RIDNUM Branch>0 SEARCH Mo v e 4(RHEAD), RHEAD not the head record Return SEARCH Mo v e RHEAD, RCURRENT LOOP Mo v e 4(RCURRENT), RNEXT Compare (RNEXT), RIDNUM Branch=0 DELETE Mo v e RNEXT , RCURRENT Branch LOOP DELETE Mo v e 4(RNEXT), R TEMP Mo v e R TEMP , 4(RCURRENT) Return Figure A subroutine for deleting a record from a linked list.

Figure Encoding instructions into 32-bit words.

Table 2.1. Generic addressing modes.

Figure 2.1. Binary, signed-integer representations.

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Figure 2.1. Binary, signed-integer representations.

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