The IBM pc convertible was the first to use 3.5-inch floppy drive,that intime become a standard.Also It was the first in IBM series that run on batteries & use Surface Mounted Devices.It Called the PC Convertible because with a few add-on modules,could become a primary desktop machine.Yet it was failed in the market cause-it was heavy,slow,no expansion port(serial,parralel) 
Like modern laptops, it featured power management and the ability to run from batteries. It was the follow-up to the IBM Portable and was model number 5140.
It utilized an Intel 80c88 CPU (a CMOS version of the Intel 8088) running at 4.77 MHz, 256 kB of RAM (expandable to 512 kB), dual 720 kB 3.5" floppy drives, and a monochrome CGA-compatible LCD screen at a price of $2,000.
It weighed 13pounds (5,8 kg) and featured a built-in carrying handle.The PC Convertible had expansion capabilities through a proprietary ISA bus-based port on the rear of the machine. Extension modules, including a small printer and a video output module, could be snapped into place. The machine could also take an internalmodem, but there was no room for an internal hard disk.
Pressing the power button on the computer did not turn it off, but put the machine into a "suspend" mode. This avoided the long process of booting up. The CMOS 80c88 CPU has a static core, which means that it can be stopped simply by stopping the system clock oscillator that is driving it, and it will hold its state indefinitely and resume processing at the point it was stopped when the clock signal is restarted, as long as it is kept powered. CMOS circuits use extremely little power when they are not changing state, so an 80c88 that is on but not being clocked uses very nearly as little as one that is powered off.
The screen was not very tall, so text characters and graphics were compressed vertically, appearing about half their normal height. The display was capable of resolutions of 80x25 (text), 640x200, and 320x200.
The machine sold very poorly for a number of reasons. The Convertible was heavy, not much faster than the Portable it replaced (despite the newer CMOS processor and use of static RAM), didn't come with traditional PC expansion ports (such as serial ports and a parallel port) without an add-on, and had a hard-to-read, oddly-shaped LCD screen (the first screens lacked a backlight). It also competed against faster portables based on the Intel 80286 that offered optional hard drives, from companies such as Compaq, and laptops from companies such as Toshiba and Zenith that were lighter and offered similar specifications, sometimes at half the price. With the screen, the keyboard was also widely criticized.
It was replaced in 1991 by the IBM PS/2 L40 SX, and in Japan by the IBM Personal System/55note, which was the predecessor to the ThinkPad.
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