Multitasking is impossible under real mode because there is no way to keep programs from interfering with each other as they use the PC's various components. The most acute form of this occurs when programs overwrite each other in memory. For example, a database program may use extra memory for sorting a database. In real mode, there is nothing to prevent another program, say, a spreadsheet, using this memory for a recalculation. When both programs try to put data in the same place, whichever program gets there first loses, since the second program writes over the data of the first. If the second program writes over some of the executing code of the first program, then not only is data corrupted, but the computer may hang since it can't continue with the first program.