Base Address

What is Base Address?

In the world of computers, the base address refers to the starting point of the memory. It is an address that references the other addresses in the memory.

Technically, it is an absolute address and is usually used as a comparative address of a particular position of a piece of data or instruction that is being worked on currently by the program.

Understanding Base Address

What is Base Address

Ideally, the base address of a memory in a computer acts as the reference point for the other data addresses stored in it. It actually signifies the commencement of a program stored in the memory.

You may think of a base address as an arrangement of a code or a signal to the program or the computer which helps in operating in a particular manner.

When an offset is added to the base address, it helps in specifying the address of each instruction stored in the memory. Similarly, it also helps in calculating the absolute address of a data set.

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In addition to that, the base address helps in relocating the memory image of a program while dynamic linking.

The base address can be referred to or can also be addressable itself. It mainly depends on the design of the hardware or software interface of the manufacturer.

The concept of a base address is nothing new. In fact, it dates back to the days of pageable memory on the mainframe, which is considered to be the earliest computational machine.

These machines typically had a limited and fixed amount of memory that allowed running only a single program at a time. As a result, the program was loaded to the same memory location, always, as the base address.

Over time, when the machines with virtual memory emerged, several programs could be run on them at the same time.

These machines typically used a page swapping process or partitions. This enabled them to load a program at any place.

All shared and executable object files should ideally consist of a base address. This is basically the bottommost virtual address related to the memory image of a particular object file of a program.

Normally, there are three specific types of values in the loadable section of the program that are used while calculating the base address of a shared and executable object file while execution. These three values are:

If you want to calculate the typical base address of a PT_LOAD segment, for example, you will have to follow these steps:

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However, you must keep in mind that the memory address thus calculated may not correspond to the p_vaddr values. This is because it entirely depends on the type of file you want to load into the memory.

Occasionally, a base address may be assigned different letters, but it is generally done in a synchronistic or repetitive fashion.

What is a Base Address Example?

Typically, a base address indicates the start of a program or each instruction in the program. These are expressed with an offset in addition to the base address.

An example of a base address would be the base address plus five. This indicates the base address of the fifth instruction.

Sometimes, specific devices, such as an external hard drive, are allocated with addresses of two, being in the second place. The program will, however, use the base address as a reference in order to find the data from it.

Also, in the case of a printer, the word processing program will try to communicate with it first prior to sending any document or set of instructions to its queue.

In this case, a base address will be allocated to the command type which will bring about a communication test. The next step will be followed only after it is confirmed that the printer is on and is ready to receive commands.

This next step of sending the command to the printer queue is recognized by the application only because the base address plus two is allocated to that specific command function.

While executing the third command, the program would once again reference the base address when the second step is completed.

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Base Address Vs Offset Address

Conclusion

Just as this article points out, a base address is the starting point or originating location that helps the computer programs to identify the commencing set of instructions within a sequence of programming commands.

It is also used sometimes to specify the location of a particular hardware component.