CSC373 Quiz 1 Answers

Answers are in red.

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1. Convert between decimal, binary, and hex representation of (non-negative) integers.

   Decimal	Binary	Hexadecimal
   31	0001 1111	0x1F
   95	0101 1111	0x5F
   90	0101 1010	0x5A

2. Evaluate the bit operations: |, &, ^, ~, <<, >> (arithmetic right shift), and ! on integers.

   Operation	Result
   a	0x00EE 00FF
   b	0x8800 66AA
   a & b	0x0000 00AA
   a | b	0x88EE 66FF
   ~b	0x77FF 9955
   !b	0x0000 0000
   a << 3	0x0770 07F8
   b >> 4	0xF880 066A
   a ^ b	0x88EE 6655
   a ^ ~b	0x7711 99AA

3. Write a C expression in terms of the int variable x with result:

   • The most significant byte is unchanged and all other bits are set to 0.
     Example: x = 0x56789ABC, result = 0x56000000
     

   Assign the expression to the int variable result.

   Rules:

   • Use only declarations of int variables and assignment statements.
   • Allowed operators: & | ^ << >> + !
   • Allowed constants: one byte integers. E.g. 0xFF.

    
    
    
    
    
    result = (~0 << 24) & x;
   or
    result = (0xFF << 24) & x;
   or
    result = (x >> 24) << 24;
   	

Challenge Problem (5 pts extra Credit)

1. Write a C expression in the int variable x that equals ~x if x is < 0 and equals x if x >= 0. Assign the expression to the int variable result.

   Rules:

   • Use only declarations of int variables and assignment statements.
   • Allowed operators: & | ^ << >> + !
   • Allowed constants: one byte integers. E.g. 0xFF.

    
    
    
    
    
    result = (x >> 31) ^ x;