FAQ.ABC

Mike Stechcae                  QB Frequently Aske Questions   mstechcae@webcity.ca           12-15-02 (  :  )       TEXT                   78   3007     faq.txt                                  Advanced QBasic FAQã                             ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄããQ. Why do I get a "String Space Corrupt" message before my program isã   supposed to end?ããA. I think Microsoft claims that it is a bug in Qbasic 1.x. To prevent ãthis from happening, declare every variable and try using fixed length ãstrings.ãããQ. What does DEFINT mean?ããA. DEF stands for Default, and INT stands for integer. After this ãstatement gets processed, Qbasic assumes that your variables are all integers.ãããQ. In some programs, I see that variables end with #, &, !, %, and $. ãWhy?ããA. This is one way to force declaration. the # means the variable is aãdouble, & means long, ! means single, % means integer, and $ means string.ãããQ. How else can I declare variables?ããA. Use DIM followed by a variable (without a symbol) followed by the ãword AS and the data type. For example, DIM b AS STRING makes the variable b ãa    string variable. This is the same as b$.ãããQ. I have assembly code in my program and when the program runs, it ãlocks up or windows gives me an error message about Qbasic.ããA. The assembly code used is incorrect. The end of the code must have ãthe machine equivalent of RETF or RETF x where x is the number of ãcharacters to return.ããQ. How do I convert assembly code to machine code?ããA. Access DEBUG.EXE. (Sorry Windows XP users, but you need the real ãDOS)and type in "a". Type in assembly commands one per line. When you ãare done, press enter twice. Now type "u 100". The column to the left of ãthe assembly codes is the actual machine code you copy. Read the column ãas if you were reading a book.ã   ãQ. Why is assembly required in some programs?ããA. It makes some operations faster, It introduces and uses new ãoperations, and the code generally runs faster. Also, the chances of getting ãerrors are usually lower.ããQ. How do I put a blue dot in the top left corner of the screen without ãusing any of the Qbasic drawing commands?ããA. First, find out the address of your video card. The address must ãallow pixel drawing. Usually it is A000:0000 or 000A0000 in windows. ãConvert it to xxxx:xxxx (which is A000:0000). The segment is the left side and ãthe offset is the right side (of the colon). Use DEF SEG=&HA000. Now ãjust type POKE 0, 1. This will make a dot with color 1 (blue) at position ã0 in video memory (which is the top left).ããQ. What does &H before something do?ããA. &H lets Qbasic know it is hexadecimal. Qbasic automatically converts ãthis to decimal. So if a = &H10, then a = 16.ããQ. What does DEF SEG do?ããA. Changes the working memory segment to whatever you specify. This is ãto be used heavily in assembly programming.ããQ. What is the difference between '$dynamic and '$static?ããA. '$dynamic makes the program use variables only when needed. This ãmethod frees memory when variables become unused. '$static makes variables always ãin use until the program ends.ã   ã