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Mode of Operation

Protected mode 4 GB 32-bit address Windows, Linux

Real-address mode 1 MB space 20-bit address MS-DOS

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Real-Address mode

1 MB RAM maximum addressable Application programs can access any area of

memory Single tasking Supported by MS-DOS operating system

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Segmented MemorySegmented memory addressing: absolute (linear) address is a

combination of a 16-bit segment value added to a 16-bit offset

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Calculating Linear Addresses

Given a segment address, multiply it by 16 (add a hexadecimal zero), and add it to the offset

Example: convert 08F1:0100 to a linear address

Adjusted Segment value: 0 8 F 1 0

Add the offset: 0 1 0 0

Linear address: 0 9 0 1 0

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Protected Mode

4 GB addressable RAM (00000000 to FFFFFFFFh)

Each program assigned a memory partition which is protected from other programs

Designed for multitasking Supported by Linux & MS-Windows

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Flat Model All segments are mapped to the entire 32-bit physical address

space of the compter.. Each segment is defined by a segment descriptor, a 64-bit value stored in a table known as the global descriptor table (GDT).

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Multi-Segment Model Each program has a local descriptor table (LDT)

holds descriptor for each segment used by the program

32-Bit Windows Programming

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Standard Console Handles

STD_INPUT_HANDLE standard input

STD_OUTPUT_HANDLE standard output

STD_ERROR_HANDLE standard error output

A handle is an unsigned 32-bit integer. The following MS-Windows constants are predefined:

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GetStdHandle

GetStdHandle returns a handle to a console stream Specify the type of handle (see previous slide) The handle is returned in EAX Prototype:

GetStdHandle PROTO,

nStdHandle:DWORD ; handle type

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ReadConsole The ReadConsole function provides a convenient

way to read text input and put it in a buffer. Prototype:

ReadConsole PROTO,

handle:DWORD, ; input handle

pBuffer:PTR BYTE, ; pointer to buffer

maxBytes:DWORD, ; number of chars to read

pBytesRead:PTR DWORD, ; ptr to num bytes read

notUsed:DWORD ; (not used)

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ReadConsole Example

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ReadConsole Example

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ReadConsole Example

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ReadConsole Example

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WriteConsole The WriteConsole function writes a string to

the screen, using the console output handle. Prototype:

WriteConsole PROTO,

handle:DWORD, ; output handle

pBuffer:PTR BYTE, ; pointer to buffer

bufsize:DWORD, ; size of buffer

pCount:PTR DWORD, ; output count

lpReserved:DWORD ; (not used)

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WriteConsole Example

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WriteConsole Example

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WriteConsole Example

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CreateFile CreateFile either creates a new file or opens an

existing file. If successful, it returns a handle to the open file; otherwise, it returns a special constant named INVALID_HANDLE_VALUE.

Prototype:

CreateFile PROTO,

pFilename:PTR BYTE, ; ptr to filename

desiredAccess:DWORD, ; access mode

shareMode:DWORD, ; share mode

lpSecurity:DWORD, ; ptr to security attribs

creationDisposition:DWORD, ; file creation options

flagsAndAttributes:DWORD, ; file attributes

htemplate:DWORD ; handle to template file

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CreateFile Example

INVOKE CreateFile,ADDR filename, ; ptr to filenameGENERIC_READ, ; access modeDO_NOT_SHARE, ; share modeNULL, ; ptr to security attributesOPEN_EXISTING, ; file creation optionsFILE_ATTRIBUTE_NORMAL, ; file attributes0 ; handle to template file

Opens an existing file for reading:

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CreateFile Example

INVOKE CreateFile,ADDR filename,GENERIC_WRITE, ; access modeDO_NOT_SHARE,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0

Opens an existing file for writing:

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CreateFile Example

INVOKE CreateFile,ADDR filename,GENERIC_WRITE,DO_NOT_SHARE,NULL,CREATE_ALWAYS, ; overwrite existing fileFILE_ATTRIBUTE_NORMAL,0

Creates a new file with normal attributes, erasing any existing file by the same name:

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ReadFile

ReadFile reads text from an input file Prototype:

ReadFile PROTO,

handle:DWORD, ; handle to file

pBuffer:PTR BYTE, ; ptr to buffer

nBufsize:DWORD, ; num bytes to read

pBytesRead:PTR DWORD, ; bytes actually read

pOverlapped:PTR DWORD ; ptr to asynch info

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ReadFile Example

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ReadFile Example

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ReadFile Example

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WriteFile WriteFile writes data to a file, using an output

handle. The handle can be the screen buffer handle, or it can be one assigned to a text file.

Prototype:WriteFile PROTO,

fileHandle:DWORD, ; output handle

pBuffer:PTR BYTE, ; pointer to buffer

nBufsize:DWORD, ; size of buffer

pBytesWritten:PTR DWORD, ; num bytes written

pOverlapped:PTR DWORD ; ptr to asynch info

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WriteFile Example

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WriteFile Example

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WriteFile Example

16-Bit MS-DOS Programming

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Interrupt

Do something else, and get interrupted when I/O events happen.

May be triggered by hardware or software.

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INT I/O Example

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INT I/O Example

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Interrupt Vector Processing

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Interrupt Vector Processing

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Common Interrupts

INT 10h Video Services INT 16h Keyboard Services INT 17h Printer Services INT 1Ah Time of Day INT 1Ch User Timer Interrupt INT 21h MS-DOS Services