How Many Memory Locations Can 20 Address Lines Reach?

The memory capacity of a system is determined by the number of address lines it has, which defines how many unique memory addresses it can access. In the case of a 20-bit address bus, it can address up to 2^20 addresses, which equals 1 megabyte (MB) of memory. This means that the system can access and store data across 1 MB of memory locations. In comparison, a 24-bit address bus can access up to 2^24 addresses, equivalent to 16 MB of memory. If you have a 32-bit address bus, it can address up to 2^32 addresses, allowing access to a vast 4 gigabytes (GB) of memory space. So, the memory capacity increases as the number of address lines grows, with 20 bits providing access to 1 MB, 24 bits to 16 MB, and 32 bits to 4 GB of memory.

The capacity of memory that a CPU can directly access depends on the width of its address bus. To illustrate, a 20-bit address bus allows the CPU to address a maximum of one megabyte (1MB) of memory. Expanding the address bus to 24 bits increases this capacity to 16 megabytes (16MB), and a 32-bit address bus extends the range to accommodate up to four gigabytes (4GB) of memory. Essentially, the address bus width determines the range of memory locations a CPU can access without the need for complex addressing schemes.

If a computer employs a 20-bit address, it can access a total of 1,048,576 different memory locations. Each of these locations represents a potential address for a memory byte. In computer lingo, this quantity, denoted as 2^20, is referred to as 1 megabyte or 1 MB of memory. In more expansive terms, a 20-bit address can be utilized to pinpoint 1 megabyte, which corresponds to 1,048,576 locations. This equates to a 4 gigabit (4 GiB) address space, totaling 4,294,967,296 different memory locations. In essence, the 20-bit address enables the computer to access and manage a vast memory space consisting of billions of memory locations.