C/C++ Programmer's Guide (G06.25+)

Using the C Run-Time Library

HP C/C++ Programmer’s Guide for NonStop Systems—429301-008

4-4

Physical File Types

As mentioned earlier, the C run-time library provides input and output access to several

types of physical files, including C files, EDIT files, processes, and terminals. The

following subsections describe these physical file types and specify which logical types

you can use to access each of the physical types.

C Files

C files are odd-unstructured disk files with a file code of 180 when stored in the

Guardian file system. Because C files are odd-unstructured (rather than simply

unstructured), they are byte-addressable; that is, you can read, write, and position to

single bytes instead of words.

When accessing a C file, you can use either the text or the binary logical type.

Opening a C file as a text file causes subsequent writes and reads to transfer the exact

number of characters specified, including trailing blanks.

Edit Files

When accessing an EDIT file, you must use the text logical type. Due to their

physical structure, EDIT files are only line-addressable. Consequently, an error occurs

if you attempt to disable line buffering of an EDIT file.

Because EDIT files do not physically contain newline characters, the run-time library

automatically adds them on input and removes them on output. This addition of

newlines makes the EDIT file truly accessible as a text file.

It is a standard feature of EDIT files that trailing blanks are stripped from each line.

Processes

When accessing a process, you can use either the binary or the text logical type.

Table 4-1. Buffer Sizes

File Type Maximum Length of Buffer in Bytes

Terminals 239

EDIT files 239

C file accessed as text-type logical file 256

C file accessed as binary-type logical file 4096

Process accessed as text-type logical file 256

Process accessed as binary-type logical file 32,767

$RECEIVE 32,767