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INFORMIX-4GLTRAINING

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Versions of Informix-4GL

»Informix-4GL Rapid Development System (RDS)

»Informix-4GL C Compiler Version

Compiling:

Rapid Development System:

Source file .4glPseudo code

C Compiler System:

Source .4gl->Intermediate fles->Executable file .4ge

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Differences b/w the two versions:

RDS C Compiler

» Compile Time Less More

» Run Time More Less

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Basic Components of Informix 4GL

»PROGRAM

»MODULE

»FUNCTION

»FORM

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Program Blocks

»MAIN

»FUNCTION

»REPORT

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Compiling .4gl in RDS System

»Creating a program from a single module

fglpc filename.4gl

»Creating a program from multiple modules

Compile each program to p-code

fglpc file1.4gl file2.4gl

Concatenate p-code files together

Cat file1.4go file2.4go >myprog.4gi

»Executing the program

fglgo filename.4go

OR

fglgo myprog.4gi

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Compiling .4gl in C Compiler version

» Creating a program from a single module

C4gl filename.4gl –o myprog.4ge

» Creating a program from multiple modules

To compile a singe module to object code

C4gl filename.4gl –o filename.o

To create an executable from multiple modules

C4gl file1.4gl file2.o file3.0 –o myprog.4ge

» Executing the program

myprog.4ge

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Sample makefile

4GL = filename.4gl filename2.4gl

FORM = formname.per

PROG_NAME = application.4ge

COBJS = $(4GL: .4gl=.o)

POBJS = $(4GL:.4gl=.4go)

FORM = $(FORM:.per=.frm)

CCODE: $(OBJS)

c4gl –o $(PROG_NAME) $(COBJS)

@-echo “Finished Compiling ccode…”

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File Extensions

Extension Description

.4gl Informix 4GL source module

.4ge C Compiled version executable

.o C Compiled version object

.4go RDS Version object

.4gi RDS Version executable

.per Form File Source

.frm Form File Compiled

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SYNTAX:

DEFINE variablename data-type

Example:

DEFINE fname CHAR(10)

DEFINE start_date DATE

DEFINE x,y,z INTEGER

(OR)

DEFINE fname CHAR(10),

start_date DATE,

x,y,z INTEGER

DEFINING VARIABLES

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Initialization of Variables

LET:

Assigns value to a variable.

Example:

LET fname = “John”

Let x = 5

Initialize:

INITIALIZE variables to NULL

Example:

INITIALIZE lname TO NULL

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Scope of Variables

»Global

»Module

»Local

EXAMPLE:

glob.4gl

GLOBALS

DEFINE var1 CHAR(1)

END GLOBALS

emp_main.4gl

GLOBALS “Glob.4gl”

DEFINE var2 SMALLINT

MAIN

DEFINE var3 INTEGER

CALL funct1()

END MAIN

FUCTION funct1()

DEFINE var4 CHAR(1)

END FUNCTION

Variable Scope

var1 Global

var2 Module

Var3 Local

var4 Local

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COMMENTS in 4GL

»A pair of hyphens or minus signs

-- this is a comment

»The pound (or sharp) symbol

# this is a comment

»Left and right braces

{ this comment

is multi-line}

»Conditional comments

--@

--#

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Decision and Looping Statements

» IF

» CASE

» WHILE

» FOR

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Decisions: IF Statement

SYNTAX:

IF ……THEN

…………..

ELSE

…….

END IF

Example :

IF var_name MATCHES “[Yy]” THEN

ERROR “Customer will be deleted.”

ELSE

ERROR “Delete cancelled.”

END IF.

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IF Within Other Statements

Syntax: IF ….THEN

IF…..THEN

……………

END IF

END IF

EXAMPLE:

IF state=“IL” THEN

IF zipcode MATCHES “601*” THEN

ERROR “City is Schaumburg”

END IF

END IF

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Decisions: CASE statement

Syntax:

CASE

WHEN {expr/Boolean-expr}

statement…..

[EXIT CASE]

………

[OTHERWISE]

statement….

[EXIT CASE]

END CASE

Example:

CASE

WHEN answervar=“Y”

MESSAGE “Answered Yes.”

WHEN answervar=“N”

MESSAGE “Answered NO.”

OTHERWISE

MESSAGE “Bad Answer.”

END CASE.

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Logical Loop: WHILE Loop

Syntax:WHILE Boolean expression

statement(s)….

[EXIT WHILE]……

[CONTINUE WHILE]…..

END WHILE

EXAMPLE:

WHILE boss_in_office = TRUE

CALL act_busy() RETURNING boss_in_office

END WHILE

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FOR Loop

Syntax:

FOR integer variable = integer expression to integer expression

[STEP integer expression]

statement……

[CONTINUE FOR]…….

[EXIT FOR]……….

END FOR

Example:

DEFINE i SMALLINT

FOR i=1 TO 10

DISPLAY “i = “, i AT i,1

END FOR

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SCREEN:

»The screen is the area of the terminal where you can display the information.

»Default size of the screen is 24*80

»Informix -4GL allows you to break the screen area into smaller sections called windows.

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WINDOW

OPEN WINDOW windowname AT screenparameters

WITH no of rows ,no of columns [ATTRIBUTE(attribute-list)]

Example:

OPEN WINDOW w_yesno AT 10,10 WITH 4 ROWS,20 COLUMNS ATTRIBUTE (BORDER)

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Screen Interaction Statements

»ERROR

»DISPLAY

»MESSAGE

»PROMPT

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MESSAGE:

Syntax:

MESSAGE display-list [ATTRIBUTE(attribute-list)]

Example:

MESSAGE “Press the first letter of an option.” ATTRIBUTE (REVERSE)

ATTRIBUTES:

UNDERLINE REVERSE INVISIBLE

BOLD BLINK NORMAL

DIM

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ERROR

Syntax:

ERROR display-list [ATTRIBUTE(attribute-list)]

EXAMPLE:

ERROR “No Rows Found.”

ATTRIBUTES:

UNDERLINE REVERSE INVISIBLE

BOLD BLINK NORMAL

DIM

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DISPLAY

Syntax:

DISPLAY “message” [AT row, column] [ATTRIBUTE (attribute-list)]

EXAMPLE:

DISPLAY “Row Added.” AT 22,3 ATTRIBUTE (reverse)

ATTRIBUTES:

UNDERLINE REVERSE INVISIBLE

BOLD BLINK NORMAL

DIM

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PROMPT

SYNTAX:

PROMPT “message” [ATTRIBUTE (attribute-list)]

FOR [CHAR] variable

[ATTRIBUTE (attribute-list)]

END PROMPT

EXAMPLE:

PROMPT “Are You Sure? Y/N”

FOR CHAR answer

ATTRIBUTES:

UNDERLINE REVERSE INVISIBLE

BOLD BLINK NORMAL

DIM

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OPTIONS

EXAMPLE:

OPTIONS

MESSAGE LINE FIRST + 2,

ERROR LINE 23,

PROMPT LINE LAST -3

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Syntax for creation and compiling of a Form

»To create a default form use

form4gl –d

»To compile a form named filename.per use

form4gl filename

The .per extension is eliminated

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FORM

»MANDATORY sections

Database section

Screen section

Attribute section

»OPTIONAL Sections

Table section

Instruction section

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Database Section

The DATABASE section identifies the database (if any) on which the form is based.

This can be any database that the engine can access, including remote databases.

The DATABASE section is required , even if the form does not reference any database tables/columns.

Syntax:

» DATABASE FORMONLY

<database name>

You can specify only one database.

Example :

» DATABASE xyz

» DATABASE xyz@server

To create a form that is not related to any database , use FORMONLY and omit the TABLES section.

Also , the table name has to be formonly in the ATTRIBUTES section for each of the field in the screen.

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ATTRIBUTE SECTION

»It links display fields to database columns by using field tags

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FORM ATTRIBUTES:

»AUTONEXT

»COLOR

»COMMENTS

»UPSHIFT

»DOWNSHIFT

»DEFAULT

»REQUIRED

»INVISIBLE

»REVERSE

»WORDWRAP

»NOENTRY

»VERIFY

»INCLUDE

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»The TABLES section lists the database tables that are referenced in the specification file.

»You must list in this section any table, view or synonym whose column is referenced in the form.

»The table CANNOT be a temporary table.

TABLE SECTION

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Instruction Section

»Used to define screen records and screen arrays

»Change the default delimiters for display fields.

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OPEN FORM

Syntax:

OPEN FORM form-name FROM form-file

Example:

OPEN FORM cust FROM “cust_form”

Cust_form :Name that you gave the form when it was created

Cust :How you will refer to the form throughout the program.

OPEN FORM only loads the form onto the memory and does not display it.

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FORM

DISPLAY FORM:

DISPLAY FORM cust

Opens the form from the memory.

CLEAR SCREEN:

Clears the form from the screen but the form still exists in the memory.

CLOSE FORM:

CLOSE FORM cust

Removes the form from the memory.