0x90

0x90 is a hexadecimal literal representing the value 144 in decimal. In computing, the 0x prefix denotes hexadecimal notation, and 0x90 is commonly encountered when working with binary data, memory dumps, and low-level programming.

In x86 machine code, the single-byte opcode 0x90 encodes the NOP instruction, which means No Operation. Executing a NOP has no effect on registers or state beyond advancing the instruction pointer. NOPs are frequently used for alignment, timing adjustments, or as placeholders during development and patching. Multiple consecutive 0x90 bytes can form a NOP sled, a technique sometimes seen in certain low-level software contexts, though this use is outside ordinary programming practice.

In character encoding contexts, the byte value 0x90 corresponds to a control character in ISO/IEC 8859-1 and related encodings, specifically a C1 control code. It is not a printable ASCII character. In Unicode, this value maps to the code point U+0090, a control character rather than a visible symbol. In UTF-8, a standalone 0x90 would be invalid; it can appear only as part of a multi-byte sequence representing other characters.

As a byte, 0x90 is part of many binary data representations, including files, network protocols, and memory layouts. Its role is context-dependent, representing either a numeric value, a control code, or an opcode within a particular instruction set.

See also: Hexadecimal notation, NOP, U+0090.