Motorola M68000 User's Guide download pdf (Page 53)

Assembler Source Format 39

15. Indicate which of the following are legal constants:

12345 $ABCD @F00 $345 @777

16. What is the character string constant for “Let’s quote’ ” ” ?

17. What is the last statement in a program?

18. Write the assembler directive to place the word constant 123 in

memory at location ALPHA.

19. Write the assembler directive to reserve 1000 bytes at location BETA.

20. Write the assembler directive to set the value of SIZE to 8.

Answers

1. No. Source line may be used to create data items or provide infor

mation for the assembler.

2. No. Comments are always optional, but it is a good idea to provide

as many comments as possible.

3. A token. Tokens are identifiers or numbers.

4. Spaces or tabs.

5. F00 is legal; 50RANGES is not legal since it starts with a digit; F1040

is legal; FULL(BYTE is not legal since a ( is not a legal character in

an identifier.

6. A machine instruction or an assembler directive.

7. An asterisk.

8. A comma.

9. When the source line consists solely of a comment.

10. Label, operation, operand, and comment.

11. The symbolic representation of a machine instruction.

12. No, the blank or tab starts a comment.

13. No, the remainder of the line is ignored.

14. 8

15. 12345 is a legal decimal constant; $ABCD is legal; @F00 is not a legal

octal (base 8) constant; $345 is not a legal binary constant because

only the digits 0 and 1 can be used with binary constants; @777 is a

legal octal constant.

16. ‘Let’ s quote’” ” ”

17. A statement with the END directive.

18. ALPHA: DC.W 123

19. BETA: DS.B 100

20. SIZE: EQU 8

1 2 ... 48 49 50 51 52 53 54 55 56 57 58 ... 255 256

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Motorola M68000 User's Guide Page 53