CS

.sas7bdat is the binary format SAS uses to store data sets. SAS is commercial statistical software with a licensing cost that prices out most individual users. The format is proprietary and undocumented by SAS, so every reader outside it, including pyreadstat, is the product of reverse engineering.

A single .sas7bdat file holds the table itself, the column metadata, and enough type information to reconstruct rows. What it does not hold is the display layer. SAS stores human-readable value labels and formats in a separate catalog file, .sas7bcat. Converting to CSV throws that layer away, because CSV has no place to put it.

Arrays store elements in contiguous memory. Access is O(1). Search and modification require iterating. This guide covers six algorithms that appear repeatedly in array problems: binary search, two pointers, sliding window, prefix sums, divide and conquer, and the Dutch national flag.

Recursion and iteration are interchangeable. Any loop can be rewritten as recursion, and any recursion can be rewritten as a loop using an explicit stack. The difference is cost. Recursion consumes the call stack and adds per-call overhead. Iteration does neither. The right choice depends on the problem structure and the language.