single digit adder

例句：

1. 1. The single-digit adder was used to calculate the total sum of the numbers on the board.
   单位数加法器被用来计算板上数字的总和。
2. 2. The single-digit adder was used in schools to teach basic arithmetic skills.
   单位数加法器在学校被用来教授基本的算术技能。
3. 3. The single-digit adder was used by engineers to design circuits for electronic devices.
   单位数加法器被工程师用来设计电子设备的电路。