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MdzoRoLA Technical Developments
UNDELETE MESSAGE FUNCTION IN PAGER
by Raymond Lau Chi Wang and Yee Hon Keong
Generally, a certain portion of a pager's main memory is allocated, dynamically or statically, for storage of pages received. Two methods are proposed to implement an UNDELETE feature for a page as follows:
(A) : Add a buffer memory to store deleted mes- sages removed by a user horn a pager's main memory.
(B) : Add two status bits or flags in a page status information to indicate deleted messages without removing the deleted messages from the main memory.
Approach (A), as shown in Figure 1, assumes that the pager has a message memory for storing a maximum of five pages and that the buffer memory has the same capacity. Both memories, the message memory and the buffer memory, are initialized to NULL upon a system reset of the pager. In Figure 1, for example, a user has deleted page 2 followed by page 5. Status and data information of page 2 and of page 5 are copied to the buffer memory. Thereafter, locations in the message memory for page 2 and
page 5 are cleared to NULL to make room for any new pages. Upon an Undelete function requested by the user, the pager scans the buffer memory and displays its contents to the user.
Approach (B), as shown in Figure 2, uses a genetic data structure for storing a page. Typical page status information includes whether a page is a tone only, duplicate, or group message. In Approach (B), the two status bits are used, for example, as follows:
1. "valid-data" bit -set to indicate there are non-NULL data that could be deleted data in a page da...
