SAS 9.4 Language Reference, 6th Edition

SAS Constants in Expressions

Definition

A SAS constant is a number or a character string that indicates a fixed value. Constants

can be used as expressions in many SAS statements, including variable assignment and

IF-THEN statements. They can also be used as values for certain options. Constants are

also called literals.

The following are types of SAS constants:

• character

• numeric

• date, time, and datetime

• bit testing

Character Constants

A character constant consists of 1 to 32,767 characters and must be enclosed in quotation

marks. Character constants can also be represented in hexadecimal form.

Using Quotation Marks with Character Constants

In the following SAS statement, Tom is a character constant:

if name='Tom' then do;

If a character constant includes a single quotation mark, enclose it in double quotation

marks. For example, to specify the character value Tom's as a constant, enter the

following:

name="Tom's"

Another way to write the same string is to enclose the string in single quotation marks

and to express the apostrophe as two consecutive quotation marks. SAS treats the two

consecutive quotation marks as one quotation mark:

name='Tom''s'

The same principle holds true for double quotation marks:

name="Tom""s"

CAUTION:

Matching quotation marks correctly is important. Missing or extraneous quotation

marks cause SAS to misread both the erroneous statement and the statements that

follow it. For example, in name='O'Brien';, O is the character value of Name,

Brien is extraneous, and '; begins another quoted string.

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Comparing Character Constants and Character Variables

It is important to remember that character constants are enclosed in quotation marks, but

names of character variables are not. This distinction applies wherever you can use a

character constant, such as in titles, footnotes, labels, and other descriptive strings; in

option values; and in operating environment-specific strings, such as file specifications

and commands.

The following statements use character constants:

• x='abc';

• if name='Smith' then do;

The following statements use character variables:

• x=abc;

• if name=Smith then do;

In the second set of examples, SAS searches for variables named ABC and SMITH,

instead of constants.

Note: SAS distinguishes between uppercase and lowercase when comparing character

expressions. For example, the character values 'Smith' and 'SMITH' are not

equivalent.

Character Constants Expressed in Hexadecimal Notation

SAS character constants can be expressed in hexadecimal notation. A character

hexadecimal constant is a string of an even number of hexadecimal characters enclosed

in single or double quotation marks, followed immediately by an X, as in this example:

'534153'x

A comma can be used to make the string more readable, but it is not part of and does not

alter the hexadecimal value. If the string contains a comma, the comma must separate an

even number of hexadecimal characters within the string, as in this example:

if value='3132,3334'x then do;

Note: Any trailing blanks or leading blanks within the quotation marks cause an error

message to be written to the log.

Numeric Constants

A numeric constant is a number that appears in a SAS statement. Numeric constants can

be presented in many forms, including

• standard notation

• scientific (E) notation

• hexadecimal notation

Numeric Constants Expressed in Standard Notation

Most numeric constants are written just as numeric data values are. The numeric

constant in the following expression is 100:

94 Chapter 6 • Expressions

part/all*100

Numeric constants can be expressed in standard notation in the following ways:

Table 6.1 Standard Notation for Numeric Constants

Numeric Constant Description

1 is an unsigned integer

–5 contains a minus sign

+49 contains a plus sign

1.23 contains decimal places

01 contains a leading zero, which is not

significant

Numeric Constants Expressed in Scientific Notation

In scientific notation, the number before the E is multiplied by the power of ten that is

indicated by the number after the E. For example, 2E4 is the same as 2x10

4

or 20,000.

For numeric constants larger than (10

32

)−1, you must use scientific notation. Additional

examples follow:

• 1.2e23

• 0.5e-10

Numeric Constants Expressed in Hexadecimal Notation

A numeric constant that is expressed as a hexadecimal value starts with a numeric digit

(usually 0), can be followed by more hexadecimal characters, and ends with the letter X.

The constant can contain up to 16 valid hexadecimal characters (0 to 9, A to F). The

following are numeric hexadecimal constants:

• 0c1x

• 9x

You can use numeric hexadecimal constants in a DATA step, as follows:

data test;

input abend pib2.;

if abend=0c1x or abend=0b0ax then do;

more SAS statements

run;

Date, Time, and Datetime Constants

You can create a date constant, time constant, or datetime constant by specifying the date

or time in single or double quotation marks, followed by a D (date), T (time), or DT

(datetime) to indicate the type of value.

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