CL Programming Review

1
CL Programming Review

• DBT544
• Database for DB2/400

2
CL Restrictions

• Only open 5 files
• Cannot update files
• Only 25 levels of nested iteration and selection
  statements
• Cannot create reports only execute them

3
Begin and end

• PGM
• Also used to include parameters passed to the
  program
• ENDPGM
• Last statement executed and control returns to
  the calling program

4
Declaring Variables

• Declaring files (DCLF)
• Specify the file name
• If more than one file used in the program than
  specify the opnid
• Limit of 5 files open in the program
• Declaring variables (DCL)
• DEC, CHAR, LGL, INT, UINT
• Date, Time, and Timestamp variables are treated
  as CHAR

5
Defining a Logical Block

• Do
• Enddo
• Can be embedded in iteration, and selection
  statements

6
Iteration

• Dowhile (condition)
• Enddo
• Tests the condition first. If the condition is
  true, then the logic block is executed.

7
Iteration

• Dountil (condition)
• Enddo
• Tests the condition after the logic block is
  executed
• In other words, the logic block is always
  executed at least once.

8
Iteration

• DOFOR variable from to by
• ENDO
• Executes the loop by checking the contents of
  variable. variable starts the the from value.
  The loop ends when variable reaches the to
  value. variable is incremented by the by
  variable. If by is left out then variable is
  incremented by 1.

9
Selection

• If (condition)
• Else
• End-if.
• Allows execution of code based on a condition.
  If the condition is false, then the else logic is
  executed.
• If statements process only one CL command if true
  and one CL command if false
• Often used in combination with the DO ENDDO logic
  block.

10
Selection

• Select
• When cond(condition 1) then(cl command)
• When cond(condition 2) then(cl command)
• Otherwise (cl command)
• Endselect
• Executes the first true condition and then exits
  the structure

11
Working with Files

• RCVF OPNID(openidname)
• Reads records from a file
• Works with database files and display files
• SNDF OPNID(openidname)
• Writes to a file
• Works only with display files
• SNDRCVF OPNID(openidname)
• Reads a record from a file
• Writes to a file
• Works only with display files
• OPNID only needed if more than one file is opened
  in the program

12
MONitoring for MeSsaGes

• MONMSG MSGID(CPF9999) EXEC(cl command)
• Used to trap error messages
• Used to avoid the Black Screen of Death

13
Indicators

• Used in display file to pass information between
  the program and the display file.
• Two types of indicators
• Response (ie function keys)
• Option (ie reverse image)

14
Happy Birthday Program

• Write an interactive program that prompts for a
  userid and sends a happy birthday greeting to
  that user. Program should terminate when F3 is
  pressed

15
CL commands for the lab

• RUNSQLSTM
• DSPOBJD
• DSPFD
• DSPDBR
• DSPOBJAUT
• RTVJOBA
• DSPSPLF