Category: Programming

Basically Structures are nothing more than collection of variables so called members. Structures allows to reference all members by single name. Variables within a structure doesn’t have to be the same type. General structure declaration: struct structure_tag_name{ type member1; type member2; … type memberX }; or struct structure_tag_name{ type member1; type member2; … type memberX } structure_variable_name; in second example we declared the variable name. Otherwise variables can be declared this way: struct structure_tag_name var1, var2,var3[3]; Members of structure can be accessed by using member operator (.). The member operator connects the member name to the structure. Lets take an example: struct position{ int x; int y; }robot; we can set robot position by using following sentence: robot.x=10; robot.y=15; or simply robot={10,15}; Structures can be nested: struct status{ int power; struct position coordinates; } robotstatus; to access robot x coordinate we have to write: x=robotstatus.coordinates.x; Actions can be taken with structures: Copy; Assign; Take its address with &; Access members. Of course you can treat a structure like a variable type. So you can create an array of structures like: struct status{ int power; struct position coordinates; } robotstatus[100]; Accessing 15th robot power would be like this: pow=robotstatus[15].power;

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Another way of controlling the LPT port under Windows 2000 and XP is using the Delphi language. In this case, library, inpout32.dll, is used, which allows controlling LPT port registers. And now how to do this from the beginning. Start Borland Delphi 7.0 and make a simple form where you can enter Data to be sent to the port, Port Address, buttons for writing to and reading from a port. If you are familiar with building forms this should be ease task. Okay, now let’s start programming; first of all wee need to include inpout32.dll in the project. For this, Delphi has several ways, but let’s stay to the easiest one when the library is in the same directory, where the project is. The header in section uses we have to place function prototypes Out32 and Inp32 with special compiler directive external, saying where to find this function.

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There are a lot of Radio amateurs that want to control external devices using computer standard ports. One of them is the COM port. Everybody wants things to be easy as people doing electronics are more hardware people, not software. COM port is more often used than LPT because COM port is more resistive to bigger loads, and there are fewer chances of failing. So if you know Visual Basic a little bit, then this shouldn’t be tough to use the MSComm Control component, located in Project->Components. You should check box MSComm Control. Later you have to add this control to the form and write some code for it.

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This is a simple routine of sending and reading a byte from the LPT1 port under Windows XP. LPT port has four types of pins: 8 output pins accessed via the DATA Port 5 input pins (one inverted) accessed via the STATUS Port 4 output pins (three inverted) accessed via the CONTROL Port The remaining 8 pins are grounded Now we are interested in Data pins.

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What are variables in the C language? Variables are simple keywords that are defined by the values. Values can be changed. Variables are like a box with some size where values like apples can be put in. So variables can be various forms and sizes, so-called variable types. Variable type is defined by a reserved word which indicates the type and size of variable identifier: unsigned char my_char; long int all_my_numbers; int number; Why do we need variables? The basic answer is that memory is limited, and the compiler needs to know much space to reserve for each variable. The coder needs to specify the variable type and its size by using one of the reserved words from the table:

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