Week 04 Weekly Test Questions

Reminder: Float Representation

Exercise Description

Your task is to add code to this function in float_exp.c:

// given the 32 bits of a float return the exponent
uint32_t float_exp(uint32_t f) {
    return 42; // REPLACE ME WITH YOUR CODE
}

The function float_exp is given the bits of a float as type uint32_t. Add code so that it returns the exponent.

In other words return the contents of bits 23-30.

This function must be implemented only using bit operations and integer comparisons.

Do not remove the bias (subtract 127) from the exponent.

Once this functions is completed, you should get output like:

./float_exp -42
float_exp(-42) returned 0x84
./float_exp 3.14159
float_exp(3.14159012) returned 0x80
./float_exp -inf
float_exp(-inf) returned 0xff

Use make(1) to build your code:

make    # or 'make float_exp'

Assumptions/Limitations/Clarifications

• You may define and call your own functions if you wish.

• float_exp should return a value between 0 and 255 inclusive.

• You are not permitted to call any functions from the C library, or to perform floating-point operations, or to use variables of type float or double, or to use multiplication or division.

• You are not permitted to change the main function you have been given, or to change float_exp' prototype (its return type and argument types).

• iff stands for if and only if.

When you think your program is working you can autotest to run some simple automated tests:

1521 autotest float_exp

give cs1521 test04_float_exp float_exp.c

Reminder: Float Representation

Exercise Description

Your task is to add code to this function in sign_flip.c:

// given the 32 bits of a float return it with its sign flipped
uint32_t sign_flip(uint32_t f) {
    return 42; // REPLACE ME WITH YOUR CODE
}

The function sign_flip is given the bits of a float as type uint32_t. Add code so that it changes the sign of the number. If it is positive it should be changed to negative. If it is negative it should be changed to positive.

In other words change (flip) bit 31.

This function must be implemented only using bit operations and integer comparisons.

Once this functions is completed, you should get output like:

./sign_flip -42
sign_flip(-42) returned 42
./sign_flip 3.14159
sign_flip(3.14159012) returned -3.14159012
./sign_flip -2.718
sign_flip(-2.71799994) returned 2.71799994
./sign_flip -inf
sign_flip(-inf) returned inf

Use make(1) to build your code:

make    # or 'make sign_flip'

Assumptions/Limitations/Clarifications

• You may define and call your own functions if you wish.

• You are not permitted to call any functions from the C library, or to perform floating-point operations, or to use variables of type float or double, or to use multiplication or division.

• You are not permitted to change the main function you have been given, or to change sign_flip' prototype (its return type and argument types).

• iff stands for if and only if.

When you think your program is working you can autotest to run some simple automated tests:

1521 autotest sign_flip

give cs1521 test04_sign_flip sign_flip.c

Download bit_rotate.c here, or copy it to your CSE account using the following command:

cp -n /web/cs1521/19T3/activities/bit_rotate/files.cp/bit_rotate.c .

Your task is to add code to this function in bit_rotate.c:

// return the value bits rotated left n_rotations
uint16_t bit_rotate(int n_rotations, uint16_t bits) {
    return 42; //REPLACE ME WITH YOUR CODE
}

The function bit_rotate is given an int n and a 16-bit value as type uint16_t. Add code so that it returns the value with its bits rotated left n times.

When rotating a 16-bit value left one position, the value of bit 15 is moved to bit 0, the value of bit 0 to bit 1, the value of 1 to bit 2 ...

For example:

./bit_rotate 5 0x0001
bit_rotate(5, 0x0001) returned 0x0020
./bit_rotate 15 0x0001
bit_rotate(15, 0x0001) returned 0x8000
./bit_rotate 18 0x0001
bit_rotate(18, 0x0001) returned 0x0004
./bit_rotate -3 0x0001
bit_rotate(-3, 0x0001) returned 0x2000
./bit_rotate 8 0x1234
bit_rotate(8, 0x1234) returned 0x3412
./bit_rotate 1 0xbeef
bit_rotate(1, 0xbeef) returned 0x7ddf
./bit_rotate 1000 0xdead
bit_rotate(1000, 0xdead) returned 0xadde
./bit_rotate -42 0xfeed
bit_rotate(-42, 0xfeed) returned 0xbb7f

Assumptions/Limitations/Clarifications

• You may define and call your own functions if you wish.

• You are not permitted to call any functions from the C library.

• You are not permitted to change the main function you have been given, or to change bit_rotate's prototype (its return type and argument types).

When you think your program is working you can autotest to run some simple automated tests:

1521 autotest bit_rotate

give cs1521 test04_bit_rotate bit_rotate.c