is a program attribute that states the virtual storage location in which the program should reside and can have one of the following values ______________________________________rmode 24 the program is designed to reside below 16mb in virtual storage vse esa will place the program below 16mb rmode any the program is designed to reside at any virtual storage location either above or below 16mb vse esa places the program above 16mb unless there is no suitable storage above 16mb available ______________________________________ programmers can specify these attributes for new programs the attributes can be added to older programs if required otherwise vse esa assigns a default value when no amode or rmode is specified at execution time there are only three valid amode rmode combinations amode 24 rmode 24 amode 31 rmode 24 and amode 31 rmode any of these the combination amode 24 rmode 24 is the default combination to ensure compatibility with older programs written with 24 bit addressing schemes in the ibm es 9000 series of computers the current addressing scheme in which a program is operating is given by the value of the a mode bit in the program status word psw the function of the psw and its a mode bit is described in more detail in the 34 ibm enterprise systems architecture 390 principles of operation 34 ibm corp 1990 ibm publication number sa22 7201 0 the value of the bit can be changed in a number of ways for example the enterprise system architecture of the ibm s 390 incorporates a number of instructions which change the value of the a mode bit during program execution these instructions allow older applications.