SAS macro High-level Knowledge points

1. As a macro function, you don't need to enclose character values in quotation marks as Step functions.

One-on-which macro language is different from SAS language is macro-variable valuesbe always text, quotatio n marks is not needed to indicate TEXR constants in the macro language.

　　EXAMPLE

Dsid=open ("sasuser.houses", "I"); /*has quotation marks, because it ' s a DATA step function*/
Dsid=open ("&mydata", "&mode");
%let dsid =%sysfunc (open (sasuser.houses, i)); /*has not quatation marks, Becauese it ' s a macro funtion*/
%let dsid=%sysfunc (Open (&mydata,&mode));

2. The compile and execute process of SAS program

STEP-1: Submitted SAS programs start in the input stack.

Step-2: The word scanner takes statements from the input stack and tokenizes the statements into the fundamental units of Words and symbols.

Step-3: The word scanner then direct the tokens to the DATA step compiler, macro processor, command processor or SCL Compi Ler

Step-4: The compiler or processor that receives the tokens checks for Synatax errors,if None is found, the step executes.

3.Understanding Tokens

The fundamental building blocks of a SAS program is the tokens that Word scanner creates from your SAS language state ments. Each word, literal string, number, and special symbol in the statement in your program is a token.

The word scanner determines that a tokens ends when either a blank was found following a token or when another token begins. The maximum of a token unber SAS is 32767 characters.

Special symbol tokens, when followed by either a letter or underscore, signal the word scanner to turn processing over to the macro processor. These characters, the ampersand (&) and the percent sign (%), is called macro triggers .

　　　

The interactive between macro-language processing and sas-language processing

When the word scanner detects a macro trigger followed by a name token that it sends what follows to the macro processor and T emporarily turn processing over the macro processor. The word scanner suspends tokenization while the macro processor completes its job. Therefore, processing of a macro language reference occurs after tokenization and before compilation.

1. As your SAS programming assistant, the macro processor Codes SAS language statements for your based on the guidelines yo U give it.

2. The macro processor take the macro language statements you write and send Non-macro text, such as SAS Language statements, back to the input stack.

3. The macro processor puts the Non-macro text that it builds back on the top of the input stack.

4. The Word scanner then resumes their work by tokenizing the Non-macro text it received from the Macro Processor.

SAS macro High-level Knowledge points