National Instruments 320682C The String Manipulation Functions, The Special Nature of the Formatting and Scanning Functions

Chapter 2 Formatting and I/O Library

•The Data Formatting function panels perform intricate formatting operations with a single

function call.

–Formatting Functions, a subclass of Data Formatting, contains function panels that

combine and format one or more source items into a single target item.

–Scanning Functions, a subclass of Data Formatting, contains function panels that

transform a single source item into several target items.

–Status Functions, a subclass of Data formatting, contains function panels that return

information about the success or failure of a formatting or scanning call.

The online help with each panel contains specific information about operating each function

panel.

The String Manipulation Functions

The functions in the String Manipulation class perform common operations such as copying one

string to another, comparing two strings, or finding the occurrence of a string in a character

buffer. These functions are similar in purpose to the standard C string functions.

The Special Nature of the Formatting and Scanning Functions

The formatting and scanning functions are different in nature from the other functions in the

LabWindows/CVI libraries. With few exceptions, each LabWindows/CVI library function has a

fixed number of parameters, and each parameter has a definite data type. Each formatting and

scanning function, however, takes a variable number of parameters, and the parameters can be of

various data types. This difference is necessary to give the formatting and scanning functions

versatility.

For instance, a single Scan function call performs disparate operations, such as the following.

• Find the two numeric values in the string:

"header: 45, -1.03e-2"

and place the first value in an integer variable and the second in a real variable.

• Take the elements from an integer array, swap the high and low bytes in each element, and

place the resulting values in a real array.

To perform these operations, each formatting and scanning function takes a format string as one

of its parameters. In effect, a format string is a mini-program that instructs the formatting and

scanning functions on how to transform the input arguments to the output arguments. For

conciseness, format strings are constructed using single-character codes. These codes are