Programming Interviews Exposed: Secrets to Landing Your Next Job, 3rd Edition

Bit Manipulation Problems

Bit manipulation problems may span the range from dead simple to extremely difficult. In some cases, a single problem covers this whole range with different solutions of increasing efficiency and complexity.

Big-Endian or Little-Endian

PROBLEM Write a C function that determines whether a computer is big-endian or little-endian.

This problem tests your knowledge of computer architectures as much as it tests your ability to program. The interviewer wants to know whether you are familiar with the term endian. If you are familiar with it, you should define it or at least try to point out the differences between big-endian and little-endian, even if you forget which is which. If you are not familiar with the term, you’ll have to ask the interviewer to explain it.

Endianness refers to the order in which a computer stores the bytes of a multibyte value. (Or technically, the units of a multiunit value — for example, the computer may use a 16-bit unit size instead of an 8-bit unit size. We restrict this discussion to 8-bit units for simplicity.) Computers use multibyte sequences to represent certain primitive data types.

The bytes within an integer can be arranged in any order, but they are almost always either least-significant byte (LSB) to most-significant byte (MSB) or MSB to LSB. Significance refers to the place value a byte represents within a multibyte value. If a byte represents the lowest place values, the byte is the LSB. For example, in the number ...