Cse 313 Final

Front 1

How many memory locations are in LC-3?

Back 1

2^16

Front 2

What is the width (in bits) of MAR and MDR in LC-3?

Back 2

16 bits

Front 3

T or F? Addressing mode is a mechanism for specifying where the operand is located

Back 3

True

Front 4

T or F? The ISA specifies items including the opcodes and addressing modes.

Back 4

True

Front 5

T or F? In a Von Neumann machine, data and instructions both reside in memory.

Back 5

True

Front 6

T or F? The set of AND, OR, NOT gates is logically complete.

Back 6

True

Front 7

T or F? The addressing mode for LEA is PC-relative

Back 7

False

Front 8

T or F? The FETCH phase is common to all instructions.

Back 8

True

Front 9

Give an instruction in LC-3 that corresponds to the pseudo-instruction CLEAR R1, which sets R1 to 0

Back 9

AND R1, R1, #0

Front 10

T or F. LEA modifies the condition code bits.

Back 10

True

Front 11

T or F. .END is an assembly language instruction

Back 11

False

Front 12

T or F. HALT is actually a TRAP instruction.

Back 12

True

Front 13

Using operate type instructions only place the value 45 in R1.

Back 13

AND R1, R1, #0

ADD R1, R1, #15

ADD R1, R1, #15

ADD R1, R1, #15

Front 14

In LC-3 all memory can be accessed with 16 bits

Back 14

True

Front 15

T or F. The .ORIG pseudo-op is translated into machine instruction.

Back 15

False

Front 16

T or F. Assembly languages are more user friendly than high level languages.

Back 16

False

Front 17

T or F. Normally the values of symbol table entries generated by .EXTERNAL are resolved in the second pass of the assembler.

Back 17

True

Front 18

T or F. The System Control Block or the Trap Vector Table is a set of memory locations which contain the starting addresses of the service routines.

Back 18

True

Front 19

T or F. Invoking a subroutine automatically saves R7, which holds the return address.

Back 19

True

Front 20

T or F. At any point there are as many frames in the stack as there are pending subroutines (including main()).

Back 20

True

Front 21

T or F. The opcode of the service routine PUTS is the same as that of the TRAP instruction.

Back 21

True

Front 22

T or F. The LC-3 uses special Memory-Mapped I/O to communicate with I/Odevices.

Back 22

True

Front 23

T or F. A computer has a 16 bit address space A[15:0]. If all addresses having bits A[15:13]=111 are reserved for I/O device registers, then the maximum number of actual word addressable memory locations is 2^16 − 2^14.

Back 23

False

Front 24

T or F. A NO OP is an assembly language instruction (not necessarily in LC3) that does nothing beyond being a place holder.

Back 24

True

Front 25

T or F. The location counter is initialized using the .ORIG assembler directive.

Back 25

True

Front 26

T or F. The location counter for an assembly program is used during the execution of the program to keep track of the location of each instruction.

Back 26

False

Front 27

T or F. The .BLKW initializes the space it allocates.

Back 27

False

Front 28

T or F. The result of the linker program is the executable.

Back 28

True

Front 29

Once a program reads a character from the KBDR, automatically KBSR[15] is ______.

Back 29

0

Front 30

What is the purpose of the .END pseudo-op? How does it differ from the HALT instruction?

Back 30

.END tells the assembler when to stop assembling. It differs from HALT because HALT is an instruction & .END is not. .END can never be executed, it doesn't stop the machine, it simply makes the assembler stop assembling.

Front 31

What is the purpose of bit [15] in the KBSR?

Back 31

Its used to check whether new characters have been received by the keyboard. If bit 15 is 0, no key has been struck since the last time the processor has read the data.

Front 32

What problem could occur if the display hardware does not check the DSR before writing to the DDR?

Back 32

It could overwrite the previous value of DDR before its displayed.

Front 33

How many TRAP service routines can be implemented in the LC-3? Why?

Back 33

256 TRAP service routines because there are 256 vector locations

Front 34

Why must a RET instruction be used to return from a TRAP routine? Why won't a BR instruction work instead?

Back 34

Using a RET instruction executes a TRAP routine & jumps to the code in the TRAP vector & copies the value into a register. Using BR instructions we won't know the return location & doesn't store the value into a register.

Front 35

How many access to memory are made during the processing of a TRAP instruction? Assume TRAP is already in the IR.

Back 35

One access to memory

Front 36

What are the defining characteristics of a stack?

Back 36

Stacks are LIFO (Last In First Out) in structure. As such, the last thing put in the stack will be the first one to get out from the stack.

Front 37

How many bits are:

int, double, and char

Back 37

int: 16 bits

double: 32 bits

char: 8 bits

Front 38

T or F. A recursive function is one that solves its task by calling itself on smaller pieces of data.

Back 38

True