diff --git a/.config/zsh/.zshrc b/.config/zsh/.zshrc
index 41ce865..5bf223a 100644
--- a/.config/zsh/.zshrc
+++ b/.config/zsh/.zshrc
@@ -4,27 +4,27 @@
 #        This file is read after .zshenv file is read.
 #
 
-# activate plugins
+# Activate plugins
 eval "$(sheldon source)"
 
-# set completions
+# Set completions
 zstyle ':completion:*' matcher-list 'm:{a-z}={A-Z}' # enable completion without distinguishing uppercase or lowercase. except for input uppercase
 
-# set emacs key bindings
+# Set emacs key bindings
 bindkey -e
 
-# set alias
+# Set alias
 alias ls='ls -FG'
 
-# set history options
+# Set history options
 export HISTFILE="${XDG_STATE_HOME}/.zsh_history"
 export HISTSIZE=3000
 export SAVEHIST=3000
 
-setopt hist_expire_dups_first # delete the oldest duplicate event first when truncating the history
-setopt hist_ignore_all_dups   # delete old history if history is duplicated
-setopt hist_ignore_dups       # don't save to history if it overlaps with the previous event
-setopt hist_save_no_dups      # discard old commands that overlap with new commands
+setopt hist_expire_dups_first # Delete the oldest duplicate event first when truncating the history
+setopt hist_ignore_all_dups   # Delete old history if history is duplicated
+setopt hist_ignore_dups       # Don't save to history if it overlaps with the previous event
+setopt hist_save_no_dups      # Discard old commands that overlap with new commands
 
 function select-history() {
   BUFFER="$(history -n -r 1 | fzf --exact --reverse --query="$LBUFFER" --prompt="History > ")"
@@ -33,9 +33,9 @@ function select-history() {
 zle -N select-history
 bindkey '^r' select-history
 
-# set tool options
+# Set tool options
 export FZF_DEFAULT_OPTS='--height 40% --reverse --border'
 
-# activate runtime
+# Activate runtime
 export PIPENV_VENV_IN_PROJECT=true  # create virtual enviroment in each project
 eval "$(mise activate zsh)"
\ No newline at end of file
diff --git a/.zshenv b/.zshenv
index e0540c8..d75f5b1 100644
--- a/.zshenv
+++ b/.zshenv
@@ -3,24 +3,24 @@
 # @brief initial setup file for both interactive and noninteractive zsh
 #
 
-# set locale
+# Set locale
 export LANG=ja_JP.UTF-8
 
-# set path
+# Set path
 export PATH="/usr/local/bin:/usr/sbin:${HOME}/bin:${PATH}"
 
-arch_type="$(arch)"
-if [ "${arch_type}" = "i386" ]; then
+readonly ARCH_TYPE="$(arch)"
+if [ "${ARCH_TYPE}" = "i386" ]; then
   eval "$(/usr/local/bin/brew shellenv)"    # for Intel
-elif [ "${arch_type}" = "arm64" ]; then
+elif [ "${ARCH_TYPE}" = "arm64" ]; then
   eval "$(/opt/homebrew/bin/brew shellenv)" # for Apple silicon
 fi
 
-# set xdg
+# Set xdg
 export XDG_CONFIG_HOME="${HOME}/.config"
 export XDG_CACHE_HOME="${HOME}/.cache"
 export XDG_DATA_HOME="${HOME}/.local/share"
 export XDG_STATE_HOME="${HOME}/.local/state"
 
-# set zdotdir
+# Set zdotdir
 export ZDOTDIR="${XDG_CONFIG_HOME}/zsh"
\ No newline at end of file
diff --git a/install.sh b/install.sh
index ef738b1..0e6ad12 100755
--- a/install.sh
+++ b/install.sh
@@ -2,31 +2,16 @@
 
 set -eu
 
-echo "Installation has started..."
-echo
-
+readonly ARCH_TYPE="$(arch)"
 readonly DOTPATH="${HOME}/share/dotfiles"
 
-# Clone repository
-if [ ! -d "${DOTPATH}" ]; then
-  git clone https://github.com/takyshu98/dotfiles.git "${DOTPATH}" # Create $DOTPATH directory at the same time
-else
-  echo "Already downloaded: ${DOTPATH}"
-  echo "Updating..."
-  git -C "${DOTPATH}" stash
-  git -C "${DOTPATH}" switch master
-  git -C "${DOTPATH}" pull origin master
-  echo
-fi
-
-cd "${DOTPATH}"
-
-readonly ARCH_TYPE="$(arch)"
-echo "My architecture: ${ARCH_TYPE}"
+echo -e "Installation has started...\n"
+echo -e "My architecture: ${ARCH_TYPE}\n"
 
 # Install Rosetta 2 for Apple silicon
 if [ "${ARCH_TYPE}" = "arm64" ]; then
   softwareupdate --install-rosetta --agree-to-license
+  echo
 fi
 
 # Install Homebrew
@@ -42,6 +27,20 @@ elif [ "${ARCH_TYPE}" = "arm64" ]; then
   export PATH="/opt/homebrew/bin:${PATH}" # for Apple silicon
 fi
 
+# Clone repository
+if [ ! -d "${DOTPATH}" ]; then
+  git clone https://github.com/takyshu98/dotfiles.git "${DOTPATH}"
+else
+  echo "Already downloaded: ${DOTPATH}"
+  echo "Updating..."
+  git -C "${DOTPATH}" stash
+  git -C "${DOTPATH}" switch master
+  git -C "${DOTPATH}" pull origin master
+  echo
+fi
+
+cd "${DOTPATH}"
+
 # Restore macOS settings
 scripts/defaults.sh
 echo
diff --git a/scripts/symlink.sh b/scripts/symlink.sh
index ef53c80..77004d1 100755
--- a/scripts/symlink.sh
+++ b/scripts/symlink.sh
@@ -1,14 +1,12 @@
 #!/bin/bash
 
-DOTPATH="${HOME}/share/dotfiles"
+readonly DOTPATH="${HOME}/share/dotfiles"
 
 if [ ! -e "${DOTPATH}" ]; then
   echo "Error: Directory does not exist: ${DOTPATH}"
   exit 1
 fi
 
-cd "${DOTPATH}" || exit 1
-
 # Make symbolic links from ~/.* to ~/share/dotfiles/.*
 for file in .??*; do
   [[ "${file}" == ".DS_Store" ]] && continue
@@ -19,7 +17,7 @@ for file in .??*; do
   ln -fvns "${DOTPATH}/${file}" "${HOME}/${file}"
 done
 
-# Make symbolic links on the basis of XDG Base Directory
+# Make symbolic links on the basis of XDG Base Directory specification
 [[ -z "${XDG_CONFIG_HOME}" ]] && XDG_CONFIG_HOME="${HOME}/.config"
 mkdir -p "${XDG_CONFIG_HOME}"
 find "${DOTPATH}/.config" -maxdepth 1 -exec ln -fvns {} "${XDG_CONFIG_HOME}" \;
@@ -34,13 +32,13 @@ mkdir -p "${XDG_DATA_HOME}"
 mkdir -p "${XDG_STATE_HOME}"
 
 # Make directories with reference to Filesystem Hierarchy Standard
-mkdir -p ~/bin # for original commands
-find "${DOTPATH}/bin/" -type f -perm 0755 -exec ln -fvns {} ~/bin/ \;
+mkdir -p "${HOME}/bin" # for original commands
+find "${DOTPATH}/bin/" -type f -perm 0755 -exec ln -fvns {} "${HOME}/bin/" \;
 
-mkdir -p ~/src # for code repositories
+mkdir -p "${HOME}/src" # for code repositories
 
-mkdir -p ~/tmp # for temporary workspace
+mkdir -p "${HOME}/tmp" # for temporary workspace
 
 ## shellcheck disable=SC2174
 ## https://github.com/koalaman/shellcheck/wiki/SC2174
-# mkdir -m 700 -p ~/.ssh
\ No newline at end of file
+# mkdir -m 700 -p "${HOME}/.ssh"
\ No newline at end of file