TOPS-20 PASCAL Language Manual - Bitsavers

INPUT AND OUTPUT
7.10 THE READ PROCEDURE
The READ procedure reads one or more file components into a variable
of the component type.
Format
where:
READ ( [file variable,TI variable name [,variable name •.. TI);
file variable
variable name
specifies the input file. If you omit the
file variable, PASCAL uses INPUT by default.
specifies the variable into which the file
component(s) are read. For a text file, many
file components can be read into one
variable.
By definition, the READ procedure
assignment statement and a GET
Thus, the procedure call
for a nontext file performs an
procedure for each variable name.
READ
(file variable, variable name);
is equivalent to
variable name := file variable~;
GET (file variable);
The READ procedure reads from the file until it has found a value for
each variable in the list. The first value read is assigned to the
first variable in the list; the second value is assigned to the
second variable, and so on. The values and the variables must be of
compatible types.
For a text file, more than one file component (that is, more than one
character) can be read into a single variable. For example, many text
file components can be read into a string or numeric variable. The
READ procedure repeats the assignment and GET process until it has
read a sequence of characters that represent a value for the next
variable in the parameter list. It continues to read components from
the file until it has assigned a value to each variable in the list.
Values from a text file can be read into variables of integer, real,
character, string, and enumerated types. In the file, values to be
read into integer and real variables must be separated by spaces or
must be put on new lines. Values to be read into character variables,
however, must not be separated because they are read literally,
character-by-character. Constants of enumerated types must be
separated by at least one space. Any other character that is invalid
in an identifier terminates the constant. Only the first 31
characters of the constant are significant; PASCAL ignores any
remaining characters.
You can use READ to read a sequence of characters from a text file
into a string (that is,a variable of type PACKED ARRAY[l •• n] OF CHAR).
PASCAL assigns successive characters from the file to elements of the
array, in order, until each element has been assigned a value. If any
characters remain on the line after the array is full, the next READ
begins with the next character on that line. If the end of the line
is encountered before the array is full, the remaining elements are
assigned spaces.
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