QuickBasicNews Issue 1: INTERRUPTS

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 · 4 years ago

 
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               ∫              INTERRUPTS                  ∫ 
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                    A QuickBasic specific article 
     
    QuickBasic includes a library called QB.QLB that allows the use 
  of three routines. These are INTERRUPT, INT86OLD, and ABSOLUTE. 
  These routines provide for the use of software-interrupts. 

    There are several types of interrupts, hardware interrupts and Software 
  interrupts.  But just what is an interrupt?  An interrupt is a signal 
  to the Central Processing Unit (CPU) to stop what ever it is doing, 
  and process the interrupt.  Information provided by processing an 
  interrupt can return valuable information about some event ( such as 
  the status of a mouse button ).  Interrupts can return information 
  at incredible speed. In a hardware interrupt, the interrupt instruction 
  comes from within the computer.  With a software interrupt, the 
  computer program starts the interrupt. If it weren't for the use of 
  interrupts the CPU would constantly be checking for external events. 
  An external event would be something like: Was the left mouse 
  button pressed ?, or was the mouse moved ?, or was the joystick 
  fire button pressed ? etc....  With interrupts, the CPU can keep 
  doing something else, and respond to an external event when it occurs. 
   
    If you are familiar with QuickBasic and are ready to learn how to  
  use interrupts, it would be helpful if you had a list of interrupts  
  and their functions. Because this list is extremely large we suggest 
  you look for the files containing these interrupt lists on your 
  local BBS systems.  Look for the file names  
   
    InterxxA.zip ø 
    InterxxB.zip ≥_______ where xx is the version number of the current    
    InterxxC.zip ≥        release ( 38 being the latest I am aware of ) 
    InterxxD.zip Ÿ  
  
    I should warn you that if you intend to print out these lists you 
  should have lots of time and printer paper ( over 1000 sheets of paper ). 
  The list is put out by Ralph Brown. The above MSDOS interrupt list 
  contains over 5900 functions available through interrupt calls on IBM  
  PCs and Compatibles. Although these lists are readily available from 
  many local BBS systems, you may want to consider the book by Ralph  
  Brown & Jim Kyle available at many bookstores. The electronic listings 
  mentioned above are a listing (in numerical order) of the interrupt 
  numbers, and does not contain an index as the book version does. Neither 
  the book version, nor the electronic listings were intended as a 
  tutorial on interrupts. The listings primarily serve as a reference 
  source to the different interrupt numbers and their functions.  The 
  Book is available at major bookstores under the name: 

                 PC Interrupts: 
                 A Programmer's Reference to Bios, DOS, and Third- 
                 Party Calls 
                 (Second Edition) 
                 Ralph Brown and Jim Kyle 
                 1210 Pages 
                 Addison - Wesley 
                 ISBN 0-201-62485-0 
                 $39.95 

    Because the interrupt lists are so long, we cannot cover all of 
  the interrupts in this publication.  Next month we will take a look 
  at some interrupt numbers and their functions and we will show how 
  to incorporate an interrupt instruction into your programming 
  code.  Once you have a basic understanding of how to use interrupts 
  you can go through an interrupt list and find the ones you will need. 

    Call Interrupt - is a statement in QuickBasic that allows BASIC    
                    programs to perform DOS system calls.  The 
                    format is as follows: 

             CALL Interrupt ( num, inregs, outregs ) 

               * where num  has a value between 0 and 255, which 
                 is the DOS interrupt number. Thus there is a 
                 possibility of 256 interrupts. 

               * where inregs contains the register values before 
                 the interrupt is performed 

               * where outregs contains the register values after 
                 the interrupt is called 

               ( registers are special places in memory where data 
                 is temporarily stored ) 

    Now, as stated above there are a possibility of 256 interrupts, 
  0 through 255.  Each interrupt can have a number of functions.  For 
  instance in next month's column one of the things we will be  
  discussing is how to obtain information about the mouse through the 
  use of interrupts.  Interrupt 33h  ( the h stands for hexadecimal ) 
  provides information about the mouse.  Function 3h of interrupt 
  33h returns information about the position of the mouse.  
  Because there are numerous functions that can return information 
  about each interrupt, there are literally thousands of functions 
  available. 
   
    Obviously with so many possibilities it becomes quite apparent  
  that we could not begin to cover them all. Next month we will take a look 
  at using interrupt 33h to control and return information about the 
  mouse.  Included will be sample code that will be easy to follow. 

    Interrupt 33h translates into interrupt 51 in decimal. If you 
  don't understand hexadecimal representations, don't worry about 
  it.  We will explain it next time.  It's not really neccesary 
  to know since the (h) lets QuickBasic know you mean hexadecimal, 
  but we will briefly cover it anyway for those that are interested. 
  Excuse me now, I think I am receiving an INTERRUPT from the wife !