Readability - Syntax Considerations

• Allowed length
• ANSI BASIC (1978): Up to 2 characters - C3, P0
• FORTRAN 77: Up to 6 characters - INTERE, PRINCI
• Connective Characters
• C++: Underscore
• LISP: Hyphen
• Pascal, Modula-2, FORTRAN 77: None!

• Reserved Words Vs Keywords
• C++: Reserved words
• FORTRAN: Keywords
• Choice of Special Words - Block delimiters
• C++: { }
• Pascal: begin ... end
• Ada, Fortran 90: end if, end loop

Form and Meaning: Similar form with multiple meanings is not readable

• static keyword in C++:
• Storage class of local variable in a function
• Scope of global variable in a file
• Data member shared among objects of a class
• GOTO statements in FORTRAN 77 (both multi-way selection statements):
• Computed GO TO

  C     STATUS MAY HAVE A VALUE OF 1, 2, 3 OR 4
        INTEGER STATUS
  
        GO TO (10, 15, 20, 30), STATUS
  
        PRINT*, 'VALUE OF STATUS IS INCORRECT'
        GO TO 100
  10    PRINT*, 'FRESHMAN'
        GO TO 100
  15    PRINT*, 'SOPHOMORE'
        GO TO 100
  20    PRINT*, 'JUNIOR'
        GO TO 100
  30    PRINT*, 'SENIOR'
  
  100
  

• Assigned GO TO

C     STATUS MAY HAVE A VALUE OF 1, 2, 3 OR 4
      INTEGER STATUS

C     LABEL HOLDS ONLY STATEMENT REFERENCES
      IF(STATUS .EQ. 1) ASSIGN 10 TO LABEL
      IF(STATUS .EQ. 2) ASSIGN 15 TO LABEL
      IF(STATUS .EQ. 3) ASSIGN 20 TO LABEL
      IF(STATUS .EQ. 4) ASSIGN 30 TO LABEL

C     EXECUTION ERROR OCCURS IF LABEL'S VALUE IS NOT IN PARENTHESIS
      GO TO LABEL, (10, 15, 20, 30)

10    PRINT*, 'FRESHMAN'
      GO TO 100
15    PRINT*, 'SOPHOMORE'
      GO TO 100
20    PRINT*, 'JUNIOR'
      GO TO 100
30    PRINT*, 'SENIOR'

100