A numeric keypad, numpad or ten key, is the small, palm-sized, seventeen key section of a computer keyboard, usually on the very far right. The numeric keypad features digits 0 to 9, addition (+), subtraction (-), multiplication (*) and division (/) symbols, a decimal point (.) and Num Lock and Enter keys. Laptop keyboards often do not have a numpad, but may provide numpad input by holding a modifier key (typically labelled “Fn”) and operating keys on the standard keyboard. Particularly large laptops (typically those with a 17 inch screen or larger) may have space for a real numpad, and many companies sell separate numpads which connect to the host laptop by a USB connection (many of these also add an additional spacebar off to the side of the number zero where the thumb is located, as well as an additional 00 key typical of modern adding machines and cash registers). It also provides a calculator-style keyboard for efficient entering of numbers. Numeric keypads usually operate in two modes: when Num Lock is off, keys 8, 6, 2, 4 act like arrow keys and 7, 9, 3, 1 act like Home, PgUp, PgDn and End; when Num Lock is on, digits keys produce corresponding digits. On Apple Macintosh computers, which lack a Num Lock key, the numeric keypad always produces only numbers. The Num Lock key is replaced by the Clear key. The arrangement of digits on numeric keypads is different from that of telephone Touch-Tone keypads, have the 1-2-3 keys on top and 7-8-9 keys on the third row, instead of the reverse used on a numeric keypad. It is thought that the layout was arranged this way for the early telephone keypads so that the addition of the alphabetical characters found on most telephones followed the digits numerically. This layout, which matches most modern calculators and cash registers, may be confusing for those who use one of these arrangements more often. Numeric keypads are useful for entering long sequences of numbers quickly, for example in spreadsheets, financial/accounting programs, and calculators. Input in this style is similar to that of a calculator or adding machine.