Data Lab: Manipulating Bits

Introduction Purpose: To be more familiar with bit-level representations of integers and floating point numbers. Individual project Programming environment Linux server: 117.16.244.185 Telnet & login with your ID & password

Handout instructions Start by copying datalab-handout.tar to a directory using the command cp /var/share/datalab-handout.tar . tar xvf datalab-handout.tar This will cause a number of files to be unpacked in the directory. The only file you need to modify is bits.c. bits.c Contains a skeleton for 15 programming puzzles. You must complete each function skeleton using only straight-line code for integer puzzles (no loops or conditionals). Only allowed 8 operators: ! ~ & ^ | + << >> You are not allowed to use any constants longer than 8 bits.

Puzzles Bit manipulations Rating: difficulty (also the number of points) Max ops: the maximum number of operators allowed to use to implement each function

Puzzles Two’s complement arithmetic

Puzzles Floating-point operations You can used standard control structures (loops, conditionals). You may use both int and unsigned data types, including arbitrary integer and unsigned constants. You may not use union, struct, or array. Any floating point operand will be passed to the function as having type unsigned, and any returned floating point value will be of type unsigned. float_neg & float_twice must handle the full range of possible argument values including NaN and infinity.

Helper programs fshow ishow Helps you understand the structure of floating point numbers. You can use fshow to see that an arbitrary pattern represents as a floating point number Example # ./fshow 2080374784 Floating point value 2.658455992e+36 Bit Representation 0x7c000000, sign = 0, exponent = 0xf8, fraction = 0x000000 Normalized. +1.0000000000 X 2^(121) ishow Helps you understand the structure of integer numbers.

Compile Switch to the handout directory and type make

Evaluation Correctness points: 41 Performance points: 30 By executing btest, points are automatically evaluated. Performance points: 30 2 points for each function satisfying the operator limits. dlc is used to evaluate the number of operators. Bonus points: 6 Student(s) who implement the functions bitCount, ilog2, and float_i2f with the smallest number of operators will be given 2 points. A student may get 6 bonus points at maximum. The number of operators should be smaller than the operator limits. It should be done during the Lab time.