The 8051 microcontroller is a single-chip, low-cost computer that can be used for various applications and embedded systems. It is also one of the most popular microcontrollers of all time due to its ease of use and wide range of features. One important aspect of this chip is its memory capacity, which includes both internal and external RAM. The 8051 microcontroller has two types of RAM: internal and external. The internal RAM of the 8051 microcontrollers is limited to 128 bytes (256 bytes if you have an 8052). This means that any data stored in internal RAM must fit within these limits. The maximum amount of external RAM that can be connected to an 8051 microcontroller is 64K (64 kilobytes). This means that up to 64K worth of data, such as program code or variables, can be stored on a separate device and interfaced with the 8051. External RAM can also be used to store large amounts of data that would otherwise not fit into the small amount available in internal RAM.