Abstract: Remote file transfer applications often involve a situation where a receiving computer (22) contains a reference file (48) that may be similar, or perhaps even identical to, a source file (46) to be transmitted by a sending computer (20). Disclosed is a file transfer method that identifies and isolates the differences between the two files, and transmits only those differences to the receiving computer. The method divides the data in the reference file into a plurality of blocks and associates each block of data with a key value. The key values are then sent to the sending computer in the form of an array. At the sending computer, a block of data at the source file is identified, its key value computed, and the key value is then compared to the keys in the array. If a match is found, an indication of such is sent to the receiving computer. Otherwise, a byte of data from the data block is sent to the receiving computer, and a subsequent block of data is identified and analyzed.

Abstract: Disclosed is a computer data interface (100) for connecting a hand-held computer (104) and a desktop computer (102). The computer data interface includes a cable having connectors at each end. A voltage conversion circuit (116) is mounted adjacent to one of the connectors. The voltage conversion circuit receives data signals from the hand-held computer and transmits the signals to the desktop computer at voltage levels compatible with the desktop computer, Similarly, the voltage conversion circuit receives signals from the desktop computer and transmits the signals to the hand-held computer at voltage levels compatible with the hand-held computer.

Abstract: Disclosed is a system of transmitting data from a sending computer (10) to a receiving computer (30) in an 8-bit parallel format. Each computer includes a parallel communications port (14 and 34) having a data output register (24 and 44), a status register (26 and 46) and a control register (28 and 48). The method includes the steps of connecting the computers, configuring the receiving computer and writing the data to be transmitted at the sending computer. The method further includes the step of determining whether the receiving computer has the ability to receive 8-bit parallel communication. A cable for providing a communication link between the two computers is also disclosed.

Abstract: A method and apparatus for transmitting data between computers. By determining an optimum time for which a sending computer (10) must set a strobe pulse on a strobe line (54) in order for a receiving computer (30) to be able to read data transmitted, the sending computer can transmit data without the need to poll an acknowledge line (56). The optimum strobe pulse duration is determined by sending a copy of a known pattern of data from the sending computer to the receiving computer using different strobe pulse durations. The receiving computer examines the received pattern of data to determine if an error occurred during transmission. If an error occurred, the sending computer sets the acknowledge line. The optimum hold time is determined to be the shortest hold time for which the sending computer can set the strobe line and the receiving computer can receive the known pattern of data without error.

Abstract: Disclosed is a system of transmitting data from a sending computer (10) to a receiving computer (30) in an 8-bit parallel format. Each computer includes a parallel communications port (14 and 34) having a data output register (24 and 44), a status register (26 and 46) and a control register (28 and 48). The method includes the steps of connecting the computers, configuring the receiving computer and writing the data to be transmitted at the sending computer. The method further includes the step of determining whether the receiving computer has the ability to receive 8-bit parallel communication. A cable for providing a communication link between the two computers is also disclosed.

Abstract: A system for data compression and decompression is disclosed. A series of fixed length overlapping segments, called hash strings, are formed from an input data sequence. A retrieved character is the next character in the input data sequence after a particular hash string. A hash function relates a particular hash string to a unique address in a look-up table (LUT). An associated character for the particular hash string is stored in the LUT at the address. When a particular hash string is considered, the content of the LUT address associated with the hash string is checked to determine whether the associated character matches the retrieved character following the hash string. If there is a match, a Boolean TRUE is output; if there is no match, a Boolean FALSE along with the retrieved character is output. Furthermore, if there is no match, then the LUT is updated by replacing the associated character in the LUT with the retrieved character.

Abstract: Disclosed is a computer data interface (6) for connecting a handheld computer (4) and a desktop computer (2). The computer data interface includes a cable (8) having connectors (10 and 12) at each end thereof. Mounted in one of the connectors is an adapter circuit for receiving data signals from the handheld computer and transmitting the signals to the desktop computer at a voltage levels compatible with the desktop computer. Similarly, the adapter circuit receives signals from the desktop computer and transmits the signals to the handheld computer at voltage levels compatible with the handheld computer. The adapter circuit is powered by the desktop computer to prevent draining the batteries of the handheld computer.

Abstract: A cable assembly including electrically isolated longer cables connected along a portion of their lengths. Serial and parallel connectors are provided at the appropriate ends of the cables while a shorter cable connects another serial connector to the serial connector at each end of one of the longer cables.