Computer hardware programe

This first lists the use of conventional memory, giving the name and size of each driver, and then lists the use of the UMA, giving the size of each free block. To load a driver into a UMB all you have to do is change DEVICE= in the CONFIG.SYS file to DEVICEHIGH=. To load other memory resident programs in a UMB you have to add LOADHIGHT to the start of the command, usually in the 
AUTOEXEX.BAT file that normally loads the program. You may notice that in neither case is there any way of indicating which UMB will be used by the DEVICHIGH=or the LOADHIGH command. The reason for this is that a very simple first-come-first-served allocation to UMBs is used. Each device driver is loaded into the largest UMB. For example, consider the effect of loading MOUSE.SYS (14.5KBytes) and SmartDrive (22 KBytes) into UMBs in different orders. If there are two UMBs available of 15 KBytes and 23 KBytes respectively, then loading MOUSE.SYS first would use up 14.5 KBytes of the 23KByte UMB leaving two UMBs of 15 KBytes and 8.5 MBytes respectively. In this case it would be impossible to load SmartDrive into the remaining UMBs. However, if SmartDrive had been loaded first then it would have used up 22 KBytes and 1 KByte respectively and MOUSE.SYS could still be loaded into the 15KByte UMB. Clearly the order that drivers and memory resident programs are loaded is crucial to the efficient utilisation of UMBS.