How do blind and deaf-blind people use computers?
Depending on the extent of vision loss, blind people might either use magnification or text-to-speech. Magnification means a certain software program on the computer magnifies everything on the screen to be large enough for the person to see. These programs often also have options for increasing contrast, inverting colors, or changing to other color layouts that make it easier for the person to see. Blind people using magnification may or may not be able to see pictures and other graphics (such as smilies). It's best just to ask them if they can.
Text-to-speech is a software that converts text on the screen into a computerized voice. While many people have a hard time understanding synthetic speech, most blind people are used to it and can understand it fine. Speech readers have limitations in what they can interpret. Blind users with speech output can't see photos, and can't read documents that are image-based, such as scanned-in PDF files or websites that are formatted in image-based formats. Special programming (called alt-text) can allow computer users to add descriptions to photos, but unless this is specifically done, most images are simply read as "image" or the file name the image was saved as.
Deaf-blind and some blind people use braille output. Braille technology is extremely expensive so it's generally only used by those who really need it, such as deaf-blind people with not enough hearing to understand speech output and blind people who have jobs that require using the phone at the same time or looking closely at coding or punctuation. Braille output uses the same software as speech output, but rather than being read in a synthetic voice, the text on the screen is displayed on an attached hardware device with braille cells, called a refreshable braille display. The pins in a braille display move up and down into braille patterns and change as the screen changes or as the blind person interacts with the computer.
Like speech output, a braille output user cannot see images or any sort of image-based output. Unlike speech readers, braille users always have access to punctuation whereas speech reader users have to change their settings to be able to hear all punctuation.
Many blind or deaf-blind people use a combination of the three above mentioned adaptive technologies, such as speech and braille side by side, or braille and magnification. This aids them in being able to have more options for interface.
How can blind people type?
Most sighted people can look at the screen and don't need to look at the keyboard because their fingers know where the keys are. The same applies for most blind people. Blind people can also feel the grooves on the F and J keys to ensure correct placement. For blind or low vision people who haven't memorized the keyboard, there are large print and braille stickers that can be placed on the keys. There are also some keyboards available with large print or braille directly on the keys.