CL PROGRAMMING REVIEWDBT544

Database for DB2/400

CL RESTRICTIONS

Only open 5 files Cannot update files Only 25 levels of nested iteration and

selection statements Cannot create reports – only execute them

BEGIN AND END

PGM Also used to include parameters passed to the

program

ENDPGM Last statement executed and control returns to

the calling program

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

DEFINING A LOGICAL BLOCK

Do

Enddo

Can be embedded in iteration, and selection statements

ITERATION

Dowhile (condition)

Enddo

Tests the condition first. If the condition is true, then the logic block is executed.

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.

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.

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.

SELECTION

SelectWhen 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

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

MONITORING FOR MESSAGES

MONMSG MSGID(CPF9999) EXEC(cl command)

Used to trap error messages Used to avoid the Black Screen of Death

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)

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

CL COMMANDS FOR THE LAB

RUNSQLSTM DSPOBJD DSPFD DSPDBR DSPOBJAUT RTVJOBA DSPSPLF