China DOS Union

Smart Use of "DEBUG" to Select a Well-Performing Monitor

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http://www.sina.com.cn 2002/10/09 13:29 CCID Net - China Computer Education News

　　By Li Bei

　　Many DIY users focus their attention on the components of the main unit when assembling a computer, such as the CPU, graphics card... but neglect an important peripheral device - the monitor. Now there are a wide variety of monitor brands, and the display effects of different cathode ray tubes (CRTs) have their own merits, making it confusing for buyers. But how to intuitively test whether the colors of the monitor are pure, whether the black and white are balanced, and whether the convergence is accurate? Although we can use the help of some software, such as Nokia Monitor Test 1.0a. However, when purchasing, few people will carry it with them, and then only rely on the user's keen eyesight for visual inspection.


　　In fact, the operating system itself comes with a convenient tool, which is DEBUG under DOS. Now I will introduce to you how to use it.

　　After booting up, enter the DOS mode (it is recommended to be in the real DOS mode, without loading any other systems and software, but it can also pass in the DOS window mode of Windows 9X; if the user is using Windows Me or Windows XP, you can click the "Start" on the taskbar, select "Run", type "DEBUG", and then click "OK", type DEBUG and press Enter. When the DEBUG horizontal line prompt appears, we can use the "F" command to directly operate on the display buffer to make the monitor display the "graphics" we need. The specific operation commands are as shown in the chart.

DEBUG Operation Command List
Serial number
Command
Graphics

1
-f b800:00 f9f 20 70
Full screen white raster

2
-f b800:00 f9f 20 40
Full screen red raster

3
-f b800:00 f9f 20 20
Full screen green raster

4
-f b800:00 f9f 20 10
Full screen blue raster

5
-f b800:00 f9f c5 07 c4 07
Full screen white cross

6
-f b800:00 f9f c5 04 c4 04
Full screen red cross

7
-f b800:00 f9f c5 02 c4 02
Full screen green cross

8
-f b800:00 f9f c5 01 c4 01
Full screen blue cross

9
-f b800:00 f9f c5 05 c4 05
Full screen purple cross

10
-f b800:00 f9f c4 07
Full screen white horizontal line

11
-f b800:00 f9f b3 07 20 07
Full screen white vertical line

12
-f b800:00 f9f 20 70 20 70 20 70 20 70 20 70 20 70 20 70 20 70 20 70
Full screen black and white alternating


　　How about, have you all seen it? It is purer, more complete, and more intuitive than the signals provided by the color TV signal generator. Everyone can test the monitor they like, try to find its "defects", and be as critical as possible, so that they can master more "bargaining chips" when bargaining with the merchant.

　　The function of the above method is to cooperate with the adjustable components such as the deflection coil, color purity magnetic ring, six-stage magnetic ring of the CRT, to help the user adjust and repair the red, green, blue static convergence, dynamic convergence, white and dark balance, color purity and other "surface" errors of the CRT, so that our color monitor can always show its "true" color.

　　After all, the monitor is one of the components that serve the longest time in the entire computer, so carefully selecting a good monitor is a key point in buying a computer.

Excellent, collected it.

This is directly operating on the hardware. There might be a risk of damaging the monitor, right??

Software cannot damage hardware. If it could, then viruses that damage hardware could be created.
The so-called CIH that was said to damage the motherboard only damages a section of program code in the BIOS and cannot damage the BIOS. It is like damaging files (programs) in the hard disk but not the hard disk itself. Damage refers to physical, irrecoverable damage!!!

Classic.

Not bad

The technology of direct screen writing is applied. Many Chinese systems use this technology, and there was also PCTools back then. When I once wrote a program without using INT10 but using direct screen writing, I didn't obviously feel much faster, but the source code became extremely long (after macro replacement).

Good stuff, but if you use this to test the monitor, the boss will be scared!!

Okay, worth collecting

```asm
mov al,ff
out 21,ah
mov ah,12h
mov bl,36h
mov al,1
int 10
mov ah,12h
mov bl,36h
mov al,0
int 10
.............................
mov al,00
out 21h,al
g
q

```

For damaged monitor:

f b800:00 f9f 20 70
mov al,ff
out 21,ah
mov ah,12h
mov bl,36h
mov al,1
int 10
mov ah,12h
mov bl,36h
mov al,0
int 10
.............................
mov al,00
out 21h,al
g
q

Good stuff, but using this to test the monitor, the boss will be scared to death : )

It's just that it will be bad if it's broken.