You are the office manager at an insurance company. You have arranged for contractors to upgrade your computer system. This means the system will be shut down for a full day.
Write a memo of 40-50 words:
informing staff of the shutdown
telling them when it will happen
asking them to prepare alternative work for the day.
from : Tom TO : all staff
date : 25/8
Because our computor system will be upgraded by the contractors on 28 AUGUEST, so the system will be shut down for a full day on that day, i ask for you prepare alternative work for the day. and the work don't use computer system .
I think you can give a good performance to me to pass the accident. 
Business writing 中尽量少使用because....so... 这样的结构，看起来不够专业，改为：As we plan to upgrade.....
有中式英文的痕迹：我要求你们。。。。改为：please prepare alternative work if you have to use the computer.
这不能算作accident, 既然已经计划好了。整句去掉。换成thank you.
From: office manager
To: all staff
Subject: the company system
I would like to notify you that the computer system of our company's will be shut down on this Tuesday for a whole day long on account of the system needs a upgrade.Therefore, please taking notice of this event in advance, in case of some potential inconveniences and troubles on Tuesday, yet prepare alternative work for that day. 
这句话看起来非常不清楚，主语在哪里?please 的后面是吗?改成：please make sure that you have prepared alternative work.
The file system will shtudown due to system maintainance next Friday.
It will take a full day to finish this job.
Please do not acccess the file server that day and backup your files one it.
够干练了，语法错误多。 Be shut down
From: office Manager
To: all staff
Subject: upgarde of computer system
As our computer system need to be upgraded, we have arranged the contarctors to upgrade the them on Wedesday. On that day all computers should be shutted down for a full day, so you need arrange some alternative work for that day.