The String is a data type used in programming to represent a sequence of characters. It is how computers store and manipulate text. A string can contain letters, numbers, symbols, punctuation, and whitespace. For example, the command SOUR:VOLT 12.5 is a string. The name "John Doe" is a string. Even a single sentence is a string.
In most programming languages, a string is enclosed in quotation marks (either single ' or double
"). Internally, a string is stored as an array or list of characters, with each character represented by its numerical code according to a standard like ASCII or Unicode. Programming languages provide a rich set of functions for manipulating strings, such as concatenating (joining) them, searching for substrings, splitting them into parts, or converting them to uppercase or lowercase.
In the context of controlling programmable instruments with text-based command languages like SCPI, strings are fundamental. The control program constructs the appropriate command as a string and then sends that string to the instrument. The instrument's firmware then receives and parses the string to determine what action to perform. Similarly, when the instrument sends back a response, it is often in the form of a string (e.g., "1.234E+01"), which the control program must then parse to extract the numerical value.