浮點數據轉換指令包括不同的浮點精度數之間的轉換，還包括整型和浮點數之間的轉化。

在了解數據轉換指令前，必須學習 IEEE 754 定義的五種舍入規則。前兩條規則舍入到最接近的值，其他的稱為定向舍入：

舍入到最接近的值

1. Round to nearest, ties to even – rounds to the nearest value; if the number falls midway, it is rounded to the nearest value with an even least significant digit.（四舍五入到最接近的值；如果數字落在中間，則會四舍五入到最接近的具有偶數最低有效數字的值）

2. Round to nearest, ties away from zero (or ties to away) – rounds to the nearest value; if the number falls midway, it is rounded to the nearest value above (for positive numbers) or below (for negative numbers).（舍入到最接近的值；如果數字落在中間，則四舍五入到上方（對于正數）或下方（對于負數）最接近的值）

定向舍入

1. Round toward 0 – directed rounding towards zero (also known as truncation).（向零定向舍入（也稱為截斷））