Substituting one character for another on a visual display unit , for example , in word processing , a cursor positioned below the character to be altered , and the desired character substituted via the keyboard 在显示器上用一个字符来替换另一个字符,例如,在字(词)处理技术中将光标置于要改变的字符下面,再通过键盘输入一个字符来替换原来的字符。